• Title, Summary, Keyword: disturbance

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Test of Intermediate Disturbance Hypothesis by Experimental disturbance Gradient in Old-Field Plant Community (묵밭에서 교란처리구배에 따른 중간교란가설의 검증)

  • 이규송;김준호
    • The Korean Journal of Ecology
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    • v.21 no.3
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    • pp.233-241
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    • 1998
  • In order to test of intermediate disturbance hypothesis that an intermediate level of disturbance maximize biodiversity and to elucidate the effect of disturbance during the early old-field succession, the response of plant community along an experimental disturbance gradient was investigated in a five-year old-field. Response of plant community along an experimental disturbance gradient was connected with light condition because artificial disturbance gradient had been treat by clipping of plants and removing of litter. Artificial disturbance in five-year old-field plant community retarded rate of succession by increasing invasion and performance of the earlier successional species in the initial and middle stage of disturbance treatment. The species richness in the blocks of intermediate disturbance level showed the peak in early and mid-summer. This result did correspond with the prediction of intermediate disturbance hypothesis.

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Periodic disturbance compensation for precision cutting in CNC machining center (CNC 공작 기계의 정밀 절삭을 위한 주기적 외란 보상)

  • Choi, Jong-Ho;Lim, Hyuk;Choi, Byung-Gap
    • 제어로봇시스템학회:학술대회논문집
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    • pp.24-27
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    • 1997
  • A periodic disturbance canceler is proposed to compensate the periodic disturbance due to cutting process in a CNC machining center. For precision cutting, the combination of a disturbance observer and a periodic disturbance canceler is desirable in order to compensate both the frictional force and the periodic disturbance. This method is implemented in a position control system of a CNC machining center in cutting process and the experimental results are described to show its effectiveness.

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Compensation of Sinusoidal Disturbance in Pendubot System using Disturbance Observer (외란 추정기를 이용한 펜듀봇 시스템의 사인파형 외란 보상)

  • Jeon, Jeong-Hyo;Kim, Cheol-Joong;Chwa, Dong-Kyoung
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.12
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    • pp.2278-2283
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    • 2010
  • This paper deals with the pendubot control using disturbance observer. Experimental results for the motion of pendubot with balancing control show that the limit cycle can be attributed to the disturbance. Therefore, we propose the disturbance compensation method using by disturbance observer to compensate for the disturbance. Through the experimental results, the effectiveness of the proposed method is verified.

Sliding Mode Control with Disturbance Observer for An Active Magnetic Bearing System (자기베어링계에서 외란 관측기를 갖는 슬라이딩모드 제어)

  • 강민식
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.53 no.6
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    • pp.408-414
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    • 2004
  • In this paper, a disturbance observer based sliding mode control is proposed to attenuate disturbance responses in an active magnetic bearing system, which is subject to base motion. An algorithm which decouples disturbance observation dynamics from sliding mode dynamics is suggested. This algorithm preserves the robustness of the sliding mode control and satisfies reachability condition in the presence of external disturbance and parameter uncertainties. Along with experimental results, it is shown that the proposed control is effective in disturbance rejection without any additive disturbance measurement.

Disturbance Observer based PID Controller for robustness enhancement of UAVs under the presence of wind disturbance (무인항공기의 내풍성 강화를 위한 제어기의 외란관측기 연구)

  • Oh, Seungjo;Lee, Dongjin
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.26 no.2
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    • pp.61-67
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    • 2018
  • This paper presents a method to apply disturbance observer to PID controller for robustness enhancement of UAVs. The system uncertainties and disturbances bring adverse effects on performance and stability of UAVs. In this paper, we estimate the acceleration disturbances using nonlinear disturbance observer, then compensate disturbances with composite controller. By employing nonlinear disturbance observer and composite controller, we have better performance and robustness than conventional PID controller. The asymptotical stability of nonlinear disturbance observer is presented through theoretical analysis. The estimation performance of nonlinear disturbance observer is evaluated by numerical simulation. And performance of disturbance observer based PID controller is evaluated by comparing the performance with conventional PID controller.

Compensation of Unknown Time-Varying Sinusoidal Disturbances in Nonlinear Systems using Disturbance Accommodation Technique (외란 보상 기법을 이용한 비선형시스템에서의 미지의 시변 사인파형 외란 보상)

  • Chwa, Dong-Kyoung
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.10
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    • pp.1844-1851
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    • 2007
  • This paper presents methods for the compensation of sinusoidal disturbances with unknown amplitude, phase, and time-varying frequency in nonlinear systems. In the previous disturbance accommodation methods, the sinusoidal disturbance with unknown time-invariant frequency was considered. In the proposed method, the disturbance with unknown time-varying frequency is compensated. As for the control structure, two control inputs are designed separately in such a way that one of them is designed for the nonlinear system control without considering the disturbance, and the other one uses the disturbance estimate obtained from the disturbance accommodating observer. The stability analysis is done considering the disturbance estimation error and the numerical simulation demonstrates the proposed approach.

Design of a Model-Based Low-Order Disturbance Observer to Estimate a Sinusoidal Disturbance with Unknown Constant Offset (미지의 상수 오프셋을 갖는 삼각함수 외란 추정을 위한 모델기반 저차 외란 관측기 설계)

  • Lee, Cho-Won;Son, Young Ik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.4
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    • pp.652-658
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    • 2016
  • In practical control systems differences between nominal and real systems arise from internal uncertainties and/or external disturbances. This paper presents a model-based low-order disturbance observer for a sinusoidal disturbance with unknown constant offset. By using the disturbance model of a biased harmonic signal, the proposed method can successfully estimate the biased sinusoidal disturbance with unknown amplitude and phase but known frequency. At the first stage of the observer design, a model-based disturbance observer is designed when all the system states are measurable. Next, a sufficient condition is presented for the proposed observer to estimate the sinusoidal disturbance with a minimal-order additional dynamics using only output measurement. Comparative computer simulations are performed to test the performance of the proposed method. The simulation results show the enhanced performance of the proposed disturbance observer.

Time-domain Approaches for Input Disturbance Observer

  • Kim, Kyung-Soo
    • 제어로봇시스템학회:학술대회논문집
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    • pp.22-25
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    • 2005
  • In the paper, algorithms for disturbance observers are newly presented in the time-domain. Attention is paid to observing a ramp disturbance by introducing an integral term to the output equation of a constant disturbance observer. In order to reduce the sensitivity to the measurement noise, the disturbance observer is combined with the state observer. It will be shown that the estimation dynamics can be arbitrarily chosen by assigning the eigenvalues of a characteristic equation. Also, we provide the analysis of observer behaviors subject to non-ramp-style disturbances. Finally, we propose the generalized disturbance observer that accurately estimates disturbances of higher order in time series expansion.

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Novel Fuzzy Disturbance Observer based on Backstepping Method For Nonlinear Systems (비선형 시스템에서의 백스테핑 기법을 이용한 새로운 퍼지 외란 관측기 설계)

  • Baek, Jae-Ho;Lee, Hee-Jin;Park, Mig-Non
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.47 no.2
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    • pp.16-24
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    • 2010
  • This paper is proposed a novel fuzzy disturbance observer based on backstepping method for nonlinear systems with unknown disturbance. Using fuzzy logic systems, a fuzzy disturbance observer with the disturbance observation input is introduced for unknown disturbance. To guarantee that the proposed disturbance observer estimates the unknown disturbance, the disturbance observation error dynamic system is employed. Under the framework of the backstepping design, the fuzzy disturbance observer is constructed recursively and an adaptive laws and the disturbance observation input are derived. Numerical examples are given to demonstrate the validity of our proposed disturbance observer for nonlinear systems.

Composition and Structure of Himalayan Oak (Quercus leucotrichophora A. Camus) Forest under Various Degrees of Disturbance

  • Prasad, Sunil;Uniyal, Pooja;Chauhan, D.S.
    • Journal of Forest and Environmental Science
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    • v.31 no.1
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    • pp.7-13
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    • 2015
  • Forest disturbance sometime considered as a tool of management as it believed that mid level disturbance constructs better micro-climatic conditions which ultimately boost up the plant diversity. The effect of different levels of disturbance on species composition and regeneration is very important. Present attempt was carried out in a temperate evergreen oak forest which was under various degree of disturbance. The study area is one of the large ranges of oak forest in Garhwal Himalaya and compensating various types of daily needs of local people. On the basis of IVI values Quercus leucotrichophora holds first position in all the disturbance zones whereas Myrica esculenta upgraded it's rank in highly disturbed zone and showed less impacted species by disturbance. Berberis aristata and Eupatorium adenophorum in shrub layer and Anaphalis adnata and Bidens pilosa in herb layer were found as disturbance friendly species because they attained higher rank in highly disturbed zone whereas Caryopteris foetida was found disturbance-sensitive in shrub layer. The banj oak regenerated well under mid disturbance as compared to no and high degree of disturbance and a sharp downfall in the species diversity was recorded with increasing magnitude of disturbance. Density-diameter curves showed a reverse trend of lower density in higher girth classes. The results of the study should be useful for the forest management strategies.