• Title/Summary/Keyword: design variations

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Long-term Monthly Variations of Tide in Pusan Harbour (부산항 조석의 장기 월별 변동 특성)

  • 김종규;강태순
    • Journal of Ocean Engineering and Technology
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    • v.16 no.2
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    • pp.6-9
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    • 2002
  • The long-term monthly variations of tide with tidal harmonic analysis in Pusan Harbour are investigated. The present spring tidal range decreased 1.4 cm and the variation of phase lag increased than 1974. The high and low water level of yearly mean sea level is show during the February to March and August to September, respectively. It is important to note that the larger lunar elliptic N2 is large in comparison with lunisolar diurnal K1 and principal lunar diurnal O1. The ratios (Correction Factors) of monthly mean sea level and the main 4 tidal constituents are evaluated to correct the shortly (monthly) observed tide for the design of harbour facilities.

Integral Sliding Mode Controller for Magnetically Suspended Balance Beam: Theory and Experimental Evaluation (자기력 부상 시스템인 평형빔의 Integral Sliding Mode 제어기 : 이론과 실험적 평가)

  • Lee, Jun-Ho;Lee, Jeong-Seok;Park, Yeong-Su;Lee, Jae-Hun;Lee, Gi-Seo
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.49 no.9
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    • pp.526-537
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    • 2000
  • This paper deals with a sliding mode controller with integral compensation in a magnetic suspension system The control scheme comprises an integral controller which is designed for achieving zero steady-steate error under step disturbance input and a sliding mode controller which is designed for enhancing robustness under plant parametric variations. A procedure is developed for determining the coefficients of the switching plane and integral control gain such that the overall closed-loop system has stable eigenvalues. A proper continuous design signal is introduced to overcome the chattering problem. The performance of a magnetically suspended balance beam using the proposed integral sliding mode controller is illustrated. Simulation and experimental results also show that the proposed method is effective under the external step disturbance and input channel parametric variations.

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An Adaptive Fuzzy Tuning Method for the Speed Control for BLDG Motor Drive (BLDC 전동기의 속도 제어를 위한 적응 퍼지 기법)

  • Kwon, Chung-Jin;Han, Woo-Yong;Kim, Sung-Joong;Lee, Chang-Goo;Lim, Jeong-Heum
    • Proceedings of the KIEE Conference
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    • 2003.07b
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    • pp.1142-1144
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    • 2003
  • This Paper presents a speed controller based on the adaptive fuzzy tuning method for brushless DC(BLDC) motor drives under load variations. Generally, the speed tracking control systems use PI controller due to its simple structure and easy of design. PI controller, however, suffers from the electrical machine parameter variations and disturbances. In order to improve the tracking control performance under load variations, PI controller of which the parameters are modified during operation by adaptive fuzzy tuning method. This method based on optimal fuzzy logic system has simple structure and computational simplicity. It needs only sample data which is obtained by optimal controller off-line. As the sample data implemented in the adaptive fuzzy system can be modified or extended, a flexible control system can be obtained. Simulation results show the usefulness of the proposed controller.

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Improvement in Control Performance of a Servo System Compensating Bandwidth Variations at Low Speed

  • Ji, Young-Eun;Park, Je-Wook;Hwang, Seon-Hwan;Baek, Kwang-Ryul;Kim, Jang-Mok
    • Journal of Power Electronics
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    • v.10 no.4
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    • pp.382-387
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    • 2010
  • This paper presents a novel design method for determining the PID gains of a speed controller for a servo system compensating variations in bandwidth at a low speed. The variations in bandwidth of a speed controller are measured at a low speed and the relationship between the bandwidth and the damping ratio are verified by determining the location of the closed loop pole. The proposed algorithm uses the z-transform of a plant and speed controller and applies the time-varying sampling method for determining the PID gains of the speed controller at low speed. The magnitude and the phase condition are considered for finding a suitable control gain. The usefulness and effectiveness of the proposed method is demonstrated through experimental results such as low speed control and robust disturbance responses.

A Study of the Visual Image by Variations in the Location of the Waistline and the Width of the Round Belt of the Basic Pants (베이직 팬츠의 허리선 위치(位置)와 라운드 벨트 폭(幅)의 변화(變化)에 따른 시각적(視覺的) 이미지)

  • Kim, Ji-Young;Lee, Jung-Soon;Han, Gyong-Hee
    • Journal of Fashion Business
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    • v.10 no.5
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    • pp.15-27
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    • 2006
  • The purpose of this study is to evaluate the differences of visual image by variations in the location of the waistline and the width of the round belt of the basic pants. The stimuli are 21 samples: 7 variations of the location of the waistline and 3 variations of the width of the belt. The data has been obtained from 35 fashion design majors. The data has analyzed by frequency, factor analysis, anova, scheffe's test and the MCA method. The visual image by the location of waistline and the width of belt are composed of 3 factors : modernity, comfort and attraction factor. In these factors, modernity factor is estimated as the most important factor. The visual image is modern and attractive as the location of waist line goes down. And when the location of waist line is in the position of natural waist belt, belt of 3.2cm width is visually effective. Belt of 4.2cm width is effective except the position of natural waist belt. The interaction effects between the location of the waistline and the width of the belt have significant differences in comfort and attraction factors. As the main effect, significant differences were observed in all of the three factors according to the location of waistline and the width of belt.

Estimation of spatial autocorrelation variations of uncertain geotechnical properties for the frozen ground

  • Wang, Di;Wang, Tao;Xu, Daqing;Zhou, Guoqing
    • Geomechanics and Engineering
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    • v.22 no.4
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    • pp.339-348
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    • 2020
  • The uncertain geotechnical properties of frozen soil are important evidence for the design, operation and maintenance of the frozen ground. The complex geological, environmental and physical effects can lead to the spatial variations of the frozen soil, and the uncertain mechanical properties are the key factors for the uncertain analysis of frozen soil engineering. In this study, the elastic modulus, strength and Poisson ratio of warm frozen soil were measured, and the statistical characteristics under different temperature conditions are obtained. The autocorrelation distance (ACD) and autocorrelation function (ACF) of uncertain mechanical properties are estimated by random field (RF) method. The results show that the mean elastic modulus and mean strength decrease with the increase of temperature while the mean Poisson ratio increases with the increase of temperature. The average values of the ACD for the elastic modulus, strength and Poisson ratio are 0.64m, 0.53m and 0.48m, respectively. The standard deviation of the ACD for the elastic modulus, strength and Poisson ratio are 0.03m, 0.07m and 0.03m, respectively. The ACFs of elastic modulus, strength and Poisson ratio decrease with the increase of ratio of local average distance and scale of fluctuation. The ACF of uncertain mechanical properties is different when the temperature is different. This study can improve our understanding of the spatial autocorrelation variations of uncertain geotechnical properties and provide a basis and reference for the uncertain settlement analysis of frozen soil foundation.

Eigenstructure Assignment Considering Probability of Instability with Flight Control Application

  • Seo, Young-Bong;Choi, Jae-Weon
    • International Journal of Control, Automation, and Systems
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    • v.5 no.6
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    • pp.607-613
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    • 2007
  • Eigenstructure assignment provides the advantage of allowing great flexibility in shaping the closed-loop system responses by allowing specification of closed-loop eigenvalues and corresponding eigenvectors. But, the general eigenstructure assignment methodologies cannot guarantee stability robustness to parameter variations of a system. In this paper, we present a novel method that has the capability of exact assignment of an eigenstructure which can consider the probability of instability for LTI (Linear Time-Invariant) systems. The probability of instability of an LTI system is determined by the probability distributions of the closed-loop eigenvalues. The stability region for the system is made probabilistically based upon the Monte Carlo evaluations. The proposed control design method is applied to design a flight control system with probabilistic parameter variations to confirm the usefulness of the method.

Low-Power Fully Digital Voltage Sensor using 32-nm FinFETs

  • Nguyen, H.V.;Kim, Youngmin
    • IEIE Transactions on Smart Processing and Computing
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    • v.5 no.1
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    • pp.10-16
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    • 2016
  • In this paper, a design for a fully digital voltage sensor using a 32-nm fin-type field-effect transistor (FinFET) is presented. A new characteristic of the double gate p-type FinFET (p-FinFET) is examined and proven appropriate for sensing voltage variations. On the basis of this characteristic, a novel technique for designing low-power voltage-to-time converters is presented. Then, we develop a digital voltage sensor with a voltage range of 0.7 to 1.1V at a 50-mV resolution. The performance of the proposed sensor is evaluated under a range of voltages and process variations using Simulation Program with Integrated Circuit Emphasis (SPICE) simulations, and the sensor is proven capable of operating under ultra-low power consumption, high linearity, and fairly high-frequency conditions (i.e., 100 MHz).

A Study on Marine Diesel Engine Speed Control by Application of H Control ($H_{\infty}$ 제어에 의한 박용디젤기관의 속도제어에 관한 연구)

  • 양주호
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.30 no.4
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    • pp.320-328
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    • 1994
  • In 1980 s to 1990 s the marine propulsion diesel engines have been developed into lower speed and longer stroke for the enegy saving (small S.F.O.C). As these new trends the conventional mechanical-hydraulic governors were not adapted to the new requirements and the digital governors have been adopted in the marine use. The digital governors usually use the control algorithms such as the PID control, optimal control, adaptive control and etc. While the engine has delay time and parameter variations these control algorithms have difficulty in considering the stability and the robustness for the model uncertainty. In this study, the $H_{\infty}$ controller design method are applied in order to design the feedback controller K(s) to the speed control of the low speed marine diesel engine, and the two-degree-of-freedom control system is constituted with $H_{\infty}$controller. By comparison of responses of the two-degree-of-freedom control system under the delay time and parameter variations is confirmed.

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2 DOF robust performance controller design for linear system with time delay and parameter uncertainty (시간지연 및 파라미터 불확실성을 갖는 선형 시스템의 2 자유도 견실성능 제어기 설계)

  • 이갑래;정은태;최봉렬;박홍배
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.1
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    • pp.43-53
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    • 1997
  • A robust stability condition for linear systems with time delay in all variables and parameter uncertainties in all system matrices is derived. Robust performance condition that accounts for robust model-matching of closed loop system and disturbance rejection is also derived. Using the robust performance condition, robust $H^{\infty}$ controller and .mu.(sgructured singular value) controller with two-degree-of-freedom(2DOF) are designed. The controller structure is considered for $H^{\infty}$ controller, while uncertainity structure is considered for .mu. controller. Using the proposed method, $H^{\infty}$ and .mu. controllers for underwater vehicle with time delay and parameter variations are designed. Simulations of a design example with hydrodynamic parameter variations and disturbance are presented to demonstrate the achievement of good robust performance.ce.

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