• Journal of Power System Engineering
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• v.3 no.1
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• pp.50-54
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• 1999

In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, if the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which integral compensation is effective only when there is modeling error for disturbance input. The present paper considers the design problem of 2DOF servosystem incorporating an observer. It is shown that if a state feedback gain and a observer gain satisfy a condition, the integral effect does not appear when modeling error or disturbance input exists. This result means that the servosystem does not behave as a 2DOF servosystem.

• Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.13-16
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• 2008

The line of sight(LOS) is affected by the vibration of spacecraft. It is necessary to predict the effect of disturbance on LOS stability. Reaction wheel assembly is anticipated to be the largest disturbance source on spacecraft. The disturbance which is occurred mainly due to the mass imbalance is analyzed with harmonic numbers. The accuracy and stability are verified by probability density function with dynamic equation of the satellite motion.

• Journal of Power Electronics
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• v.2 no.1
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• pp.55-66
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• 2002

A new on-line dead-time compensation method for a permanent magnet (PM) synchronous motor drive is proposed. Using a simple disturbance observer without any additional circuit and off-line experimental measurement, disturbance voltages in the synchronous reference dq frame caused by the dead time and non-ideal switching characteristics of power devices are estimated in an on-line manner and fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Simulations and experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method.

• Journal of Power Electronics
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• v.6 no.3
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• pp.264-270
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• 2006

Magnetic levitation transfer systems are useful for transfer tools in clean rooms and positioning control systems with high precision because of frictionless characteristics. In this paper, the new method is proposed which is a sensorless position. At first, the magnetic levitation is performed by state feedback control with a disturbance observer for each of six axes of the movement of a levitated vehicle. The position of the vehicle is then estimated as the disturbance term of a disturbance observer for a pitch angle which is one of the control axes for the magnetic levitation. In addition, the positioning force is generated by the pitch angle control which gives a tilt to the levitated vehicle so that it generates the horizontal component of force.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2046-2048
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• 2003

In this paper, a neural disturbance observer(NDO) is developed and its application to the control of a nonlinear system with the internal and/or external disturbances is presented. To construct the NDO, a parameter tuning method is proposed and shown to be useful in adjusting the parameters of the NDO. The tuning method employes the disturbance observation error to guarantee that the NDO monitors unknown disturbances. Each of the nodes of the hidden layer in the NDO network is a radial basis function(RBF). In addition, the relationships between the suggested NDO-based control and the conventional adaptive controls reported in the previous literatures are discussed. And it is shown in a rigorous manner that the disturbance observation error converges to a region of which size can be kept arbitrarily small. Finally, an example and some computer simulation results are presented to illustrate the effectiveness and the applicability of the NDO.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.66-71
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• 2017

In this paper, we study the robustness of disturbance observer based controller for DC motor in the presence of unmodeled dynamics. It is well known that the robustness property usually becomes weaker as the control gain becomes larger. On the contrary to this expectation, it is shown that the phase margin of DOB controller remains quite a large value even though the time constant of Q-filter becomes smaller. The computer simulation results show that DOB controller is able to stabilize the motor system even in the presence of unmodeled dynamics. On the contrary, the unity-feedback system fails to maintain stability when a high gain feedback is employed for the purpose of achieving better disturbance attenuation performance.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.1027-1034
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• 2016

This paper proposes a sum of squares (SOS) method for anti-swing control of overhead crane system using HOSM (High-Order Sliding-Mode) observer. By representing the dynamic equations of overhead crane as the polynomial dynamic equations via Taylor series expansion, the control input is obtained from the converted polynomial dynamic equations by numerical tool SOSTOOL. Since the actual crane systems include disturbance such as wind and friction, we propose a method to compensate for the disturbance by estimating the disturbance using HOSM observer. Numerical simulations show the effectiveness and the applicability of the proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.34.2-34
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• 2001

There are many control methods guaranteeing the robustness of systems. Among them, H$\infty$ control, sliding mode control and disturbance observer have been used widely. Especially, disturbance observer(DOB) is one of the most popular methods because it is easy to apply and the cost to pay is low due to its simplicity. Conventional DOB utilizes output signal as a feedback signal. But in Optical Disk Drive(ODD) systems, the Position Error Signal(PES) is the only available one. So conventional DOB is not applicable. If we use error signal in stead of output signal, another form of DOB is made. We call it as Error based Disturbance Observer(EDOB). We show in this paper the difference between two systems, namely conventional DOB system and the EDOB system, and also show the effectiveness of EDOB through experiment.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.2
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• pp.69-77
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• 2019

This study introduces MATLAB Graphical User Interface (GUI)-based software to monitor ionospheric disturbances. This software detects ionospheric disturbances using Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) measurements, and estimates a location of the disturbance source through the detected disturbance. In addition, this software includes a sky plot making function and frequency analysis function through wavelet transform. To evaluate the performance of the developed software, data of 2011 Tohoku earthquake in Japan were analyzed by using the software. The analysis results verified that the ionospheric disturbances were detected through GPS and GLONASS measurements, and the location of the disturbance source was estimated through the detected disturbance.

• Journal of IKEEE
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• v.13 no.1
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• pp.36-40
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• 2009

In control of time delay systems, if the informations about the system model and the disturbance can be estimated exactly, the ideal response can be achieved by using Smith predictor controller. Therefore, in this paper, an adaptive algorithm is proposed to control time delay systems existing modelling errors and disturbance. An adaptive observer to estimate disturbance and system model is designed and adaptive laws adjusting the observer are proposed. The new Smith predictor controller is designed using the proposed adaptive observer. As a result, the proposed controller can eliminate the effects of the disturbance and the modelling error. The effectiveness and the improved performance of the proposed system are verified by computer simulation.