• Title/Summary/Keyword: Slowly Varying System

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On a Stability Property of Nonlinear Systems with Periodic Inputs Having Slowly Varying Average (주기적인 입력의 평균이 느리게 변하는 비선형 시스템의 안정성)

  • Choi Yong-un;Seo J.H.;Shim Hyungbo
    • Journal of Institute of Control, Robotics and Systems
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    • v.11 no.4
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    • pp.284-289
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    • 2005
  • It is known that, if an equilibrium of a nonlinear system has a stability property when an external input is frozen, then the property is maintained under the input being slowly varying. In this paper, we show that the same stability property is preserved not only under slowly varying input but also under slowly-varying-average input (which is not actually slowly varying but its ‘average’ is slowly varying) The input is assumed to be periodic and to vary sufficiently fast. We prove the claim by the average theory and some previous results on the slowly varying inputs.

Robust adaptive control of linear time-varying systems which are not necessarily slowly varying

  • Song, Chan-Ho
    • 제어로봇시스템학회:학술대회논문집
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    • 1990.10b
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    • pp.1424-1429
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    • 1990
  • This paper presents an indirect adaptive control scheme for discrete linear systems whose parameters are not necessrily slowly varying. It is assumed that system parameters are modelled as linear combinations of known bounded functions with unknown constant coefficients. Unknown coefficients are estimated using a recursive least squares algorithm with a dead zone and a forgetting factor. A control law which makes the estimated model exponentially stable is constructed. With this control law and a state observer, all based on the parameter estimates, it is shown that the resulting closed-loop system is globally stable and robust to bounded external disturbances and small unmodelled plant uncertainties.

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Transient Surge Motion of A Turret Moored Body in Random Waves (불규칙파 중에 Turret 계류된 부유체의 천이운동해석)

  • 김동준
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.3 no.2
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    • pp.92-99
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    • 1991
  • A moored body in the sea is subjected to second-order wave forces as well as to linear oscillatory ones. The second-order farces contain slowly-varying components, of which the characteristic frequency can be as low as the natural frequency of horizontal motions of the moored body. As a consequence, the slowly-varying force can excite unexpectedly large horizontal excursion of the body, which may cause a serious damage on the mooring system. In design analysis of Turret-type mooring system which is one of the interesting mooring systems for a floating body. the slowly-varying drift forces and the transient motion of the system during weathervaning are very important. In this paper the slowly-varying drift forces were calculated by using the Quadratic Transfer Function with considering the second order free-wave contributions. Additionaly the transient surge motion of the moored body was simulated with including the roll of the time-memory effect. In this simulation the spring constant of the spread Turret mooring system is updated at every time step for considering the nonlinear effect.

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Real-time recursive identification of unknown linear systems (미지의 선형 시스템에 대한 실시감 회귀 모델링)

  • 최수일;김병국
    • 제어로봇시스템학회:학술대회논문집
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    • 1992.10a
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    • pp.548-553
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    • 1992
  • In this paper and recursive version of orthogonal ARMA identification algorithm is proposed. The basic algorithm is based on Gram-Schmidt orthogonalization of automatically selected basis functions from specified function space, but does not require explicit creation of orthogonal functions. By using two dimensional autocorrelations and crosscorrelations of input and output with constant data length, identification algorithm is extended to cope slowly time-varying or order-varying delayed system.

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On-Line Identification Algorithm of Unknown Linear Systems (미지의 선형 시스템에 대한 On-Line 모델링 알고리즘)

  • 최수일;김병국
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.31B no.4
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    • pp.48-54
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    • 1994
  • A recursive on-line algorithm with orthogonal ARMA identification is proposed for linear systems with unkonwn time delay, order, and parameters. The algorithm is based on the Gram-Schmidt orthogonalization of basis functions, and extendedto recursive form by using two dimensional autocorrelations and crosscorrelations of input and output with constant data length. The proposed algorith can cope with slowly time-varying or order-varying delayed system. Various simulations reveal the performance of the algorithm.

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Model Reference Adaptive Control of a Time-Varying Parabolic System

  • Hong, Keum-Shik;Yang, Kyung-Jinn;Kang, Dong-Hunn
    • Journal of Mechanical Science and Technology
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    • v.14 no.2
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    • pp.168-176
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    • 2000
  • Related to the error dynamics of an adaptive system, averaging theorems are developed for coupled differential equations which consist of ordinary differential equations and a parabolic partial differential equation. The results are then applied to the convergence analysis of the parameter estimate errors in the model reference adaptive control of a nonautonomous parabolic partial differential equation with lowly time-varying parameters.

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An Empirical Study on Effect of Time-Varying Quality Chang on Apple Shipment Volume for Shipment Decision Making System (출하의사결정시스템에 있어 품질변화효과가 출하량에 미치는 영향에 대한 실증연구)

  • Xue Wang;Youngsik Kwak;Jaewon Hong
    • Journal of Platform Technology
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    • v.11 no.4
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    • pp.62-70
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    • 2023
  • This research is one of a series of studies to develop a system to help agricultural producers and sellers determine when and how much to ship products to the wholesale market to maximize their profit. The purpose of this research is to incorporate the time-varying quality change effect, which was not used in the previous agricultural and marine product shipping model. The researchers developed four models to measure the quality change effect: quality declining steadily over time, quality declining rapidly at first and then slowly, quality declining first slowly and then rapidly, and quality rising over time and then decreasing again. According to the results of an empirical analysis of the effect of each model's quality change effect on shipments for apples traded in the Garak Wholesale Market from 2014 to 2021, statistical significance was found in the quality change effect of all four models. And there was no significant difference in explanatory power between the four models. Therefore, any of the four models should be introduced into the decision-making system for shipping time for apples.

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Sliding Mode Adaptive Control of the Gunner's Primary Stabilized Head Mirror (포수 조준경 안정화 장치의 슬라이딩 모드 적응 제어기 설계)

  • Keh, Joong-Eup;Sung, Ki-Jong;Lee, Won-Gu;Lee, Man-Hyung
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.10
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    • pp.109-117
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    • 1999
  • In this paper, a direct adaptive control, based on Lyapunov Function Candidate, is applied to a nonlinear Gunner's Primary Stabilized Head Mirror system to derive a parameter adaptation scheme; furthemore, a nonlinear sliding mode control, but also compensating the error in identification of the parameters which are even varying of have uncertain values. The performance of the adaptive controller is determined by the tracking ability to a desired model under some disturbances and the slowly varying parameters of the system. Both adaptive scheme and sliding mode play an important fole in the improvement of the nonlinear system control.

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On-line self-tuning PID power controller using fuzzy logic for CDMA cellular systems (퍼지 논리를 이용한 온라인 자기동조기능을 갖는 CDMA 셀룰러 시스템용 PID 전력제어기)

  • 김상민;한진욱;김성중
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.211-214
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    • 1997
  • This paper applies fuzzy self-tuning PID controller in DS/CDMA cellular system. Power control is essential in DS/CDMA to compensate for the differing received powers due to both the slowly varying long-term and fast varying short-term fading processes and co-channel interference. The controller proposed is adaptable for the variations of the system dynamics and especially for the variable time delay which exists in mobile radio systems. Accordingly the results is the smaller power control error, that is, the smaller average transmitting power of mobile compared with the conventional control schemes. Because interferences to the other mobiles are reduced, the capacity of CDMA can be increased.

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A Study on the Active Noise Control Algorithm for Rreducing the Computation Rime (계산속도를 증가시키기 위한 능동소음제어 알고리즘에 대한 연구)

  • 박광수;박영진
    • 제어로봇시스템학회:학술대회논문집
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    • 1993.10a
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    • pp.699-703
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    • 1993
  • When the error path can be modeled as a pure delay, an adaptive algorithm for slowly time varying system is proposed to minimize the sound pressure level. This algorithm makes it possible to use the fittered-x LMS algorithm with on-line delay modeling of the error path. Another simple adaptive algorithm for pure tone noise is proposed which eliminates the cross term in the multiple error filtered-x LMS algorithm.

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