• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1247-1253
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• 2008

A design method of a T-S fuzzy model based reduced order nonlinear unknown input observer(NUIO) is presented. The fuzzy NUIO is designed based on the parallel distributed compensation(PDC) concept. It consists of a number of the linear UIOs, each of which is designed for each local linear model in the T-S fuzzy model of a class of nonlinear systems. The fuzzy NUIO provides not only the state estimates insensitive to the unknown inputs, for example, disturbances and faults etc., but also the estimates of the unknown inputs. Therefore, It can be employed in the state feedback control and disturbance rejection control of a class of nonlinear systems with unknown disturbances. It also applied to the robust residual generation for the fault detection and isolation systems and to the design of fault tolerant control systems. As an example, the NUIO is applied to an inverted pendulum system to show the state and disturbance estimation performance and to illustrate the fuzzy reduced order NUIO design method.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.4
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• pp.435-445
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• 2019

Ball screw drives are widely used in industry, and many studies have been devoted on precise, fast and robust control of ball screw drives. In this study, a novel position control algorithm for ball screw drives is proposed, which consist of a PD controller, a friction feedforward and a disturbance observer. The dynamics and the position error of such controller are analyzed to establish an error model, which can be used to predict the resulting position error of the given desired trajectory. Using the proposed error model, the desired trajectory can be modified so that the predicted position error can be compensated in a feedforward manner. The proposed algorithm does not require the model of the system for the error prediction, and thus can be easily applied to conventional control systems. The performance of the system is verified through simulations and experiments.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.3
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• pp.93-102
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• 2016

An invasive disturbance species has caused harm to biodiversity and ecosystem. To address the issue, identifying the characteristics of a habitat for invasive disturbance species is considered for forest management. This study analyzed a status of plant species by field survey based on belt transect method in the capital areas and established a predictive model for invasive disturbance species by logistic regression. As results of the study, the number of herb, vine, and invasive disturbance species and a canopy cover of tree would decrease from the forest edge to core areas (p<0.001). The predictive model was derived with variables of altitude, Topographic Wetness Index, distance to forest edge, and canopy cover of tree. It can be useful in estimating the presence or absence of species and predicting its spatial distribution. Further studies are needed to identify the pathway of introduction, spread, and possibility of germination for understanding the status of invasive disturbance species in more depth.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.4 s.235
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• pp.591-599
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• 2005

This paper proposes a systematic design methodology for high-speed/high-precision servomechanisms by using a disturbance observer. A multiplicative uncertainty model and a two degree-of-freedom controller composed of a disturbance observer (DOB) and a PD controller are considered as subsystems. Analysis of the system performance, such as internal stability and bandwidth of a servomechanism according to subsystem parameters is conducted for better understanding of the dynamic behavior and interactions among the subsystem parameters. Then, an integrated design methodology, where the interactions are considered simultaneously, is applied to design processes of the servomechanism. The tradeoff relationship between disturbance suppression and measurement noise rejection of the DOB is considered through the design process. Numerical case studies show the improved possibility to evaluate and optimize the dynamic motion performance of the servomechanism. Moreover, the disturbance observer designed based on the proposed design methodology yields excellent disturbance suppression performance.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.10
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• pp.826-832
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• 2016

A two-wheeled balancing mobile robot (TWBMR) has the characteristics of both nonlinear and underactuated system. In this paper, the disturbances acting on a TWBMR are classified into body disturbance and wheel disturbance. Additionally, we describe a nonlinear disturbance observer, which is suitable as a single input multi-output (SIMO) system for the longitudinal motion of TWBMR. Finally, we propose a reasonable disturbance compensation technique that combines the indirect reference input of equilibrium point and the direct torque compensation input. Simulations and experimental results show that the proposed disturbance compensation method is an effective way to achieve robust postural stability, specifically on inclined terrains.

• Journal of the Korean Mathematical Society
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• v.50 no.1
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• pp.17-39
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• 2013

The study of nonlinear discrete-time control dynamical systems with disturbance is an important topic in control theory. In this paper, we concentrate our efforts to multiple valued iterative dynamical systems, which model the nonlinear discrete-time control dynamical systems with disturbance. After establishing the validity of such modeling, we study the invariant set theory of the multiple valued iterative dynamical systems, including the controllability/reachablity problems of the maximal invariant sets.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.639-642
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• 1988

In this paper, the problem of regulation in the presence of a known firing disturbance is considered. We show how one can apply a disturbance-utilizing control(DUC) theory to a actual gun servo model. Applied disturbance-utilizing control theory is established by combining LQ regulator and reduced order observer in the discrete time domain. To see the performance of the applied method, computer simulation results are given.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.452-457
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• 2003

An add-on type output regulator is proposed in this paper. By an add-on controller we mean an additional controller which operates harmonically with a pre-designed one. The role of the add-on controller is to reject a sinusoidal disturbance of unknown magnitude and phase but with known frequency. Advantages of the proposed controller include that (1) it can be used only when the performance of disturbance rejection needs to be enhanced, (2) when it is turned on or off, unwanted transient can be avoided (i.e., bumpless transfer), (3) it is designed for perfect disturbance rejection not just for disturbance reduction, (4) ability for perfect rejection is preserved even with uncertain plant model. This design may be promising for optical disc drive (ODD) systems in which disc eccentricity results in a sinusoidal disturbance. For ODD systems, the sensitivity function obtained by the pre-designed controller, which may have been designed by the lead-lag, $H_{\infty}$, or DOB (disturbance observer) technique, does not change much with the add-on controller except at the frequency of the disturbance. Since the add-on controller does the job of rejecting major eccentricity disturbance, the gain of the pre-designed controller does not have to be too high.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.5
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• pp.5-14
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• 2003

Tracking control schemes on the precise mechanical system in presence of nonlinear dynamic friction is proposed. A nonlinear dynamic friction is regarded as the bristle friction model to compensate fer effects of friction. The conventional SMC method often shows poor tracking performance in high-precision position tracking application since it cannot completely compensate for the friction effect below a certain precision level. Thus to improve the precise position tracking performance, we propose the SMC method combined with the disturbance observer having tunable transient performance. Then this control scheme has the high precise tracking peformance as well as a good transient response when it is compared with the conventional SMC method and the similar types of observers, The experiment on the XY ball-screw drive system with the nonlinear dynamic friction confirms the feasibility of the proposed control scheme.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.988-992
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• 2007

Recently, dynamic system has been enlarged and is exposed to various types of disturbance. Thus designing controller for those dynamic system under random disturbance is not practically easy. As a result, the exact analysis for the system which is exposed to various irregular disturbance is quite important. In order to perform analysis, conventional BMR(Balanced Model Reduction) method is applied to moment equation in stochastic domain and reliable reduced order system model has been obtained.