• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.4
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• pp.385-391
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• 2014

This paper proposes fuzzy disturbance observer based multiple sliding surface control scheme for nonlinear systems with mismatched disturbance. In order to stabilize nonlinear systems with mismatched disturbance, a controller based on multiple sliding surface control scheme is designed. In addition, a fuzzy disturbance observer is used to estimate the disturbance. Using the fuzzy disturbance observer, "explosion of terms" problem and chattering problem were solved. The stability of the proposed control scheme is analyzed by Lyapunov stability theory. For the verification, we apply the proposed method to numerical examples and compare its result with that of the applied nonlinear disturbance observer based sliding mode control.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.372-378
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• 2012

This paper deals with a 3-phase voltage disturbance generator for a performance test of custom power devices such as dynamic voltage restorers (DVR), dynamic uninterruptable power supplies (UPS), etc. The operating principle of the proposed circuit is described in each mode of voltage sag, swell, outage, and unbalance. The main components of the proposed disturbance generator are silicone controlled rectifier (SCR) thyristors, variable autotransformers, and transformers. Therefore, the disturbance generator can be implemented with a considerably low cost compared to the conventional pulse width modified (PWM) inverter and converter type generators. Furthermore, it has good features of high reliability with simple structure, high efficiency caused by no PWM switching of the SCR thyristors, and easy control with a wide variation range. To verify the validity of the proposed scheme, simulations and experiments are carried out.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.5
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• pp.346-352
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• 2016

This paper proposes an adaptive robust control method for an acrobot system in the presence of input disturbance. The acrobot system is a typical example of the underactuated system with complex nonlinearity and strong dynamic coupling. Also, disturbance can cause limit cycle phenomenon which appears in the acrobot system around the desired unstable equilibrium point. To minimize the effect of the disturbance, we apply a fuzzy disturbance estimation method for the swing-up and balancing control of the acrobot system. In this paper, both disturbance observer and controller for the acrobot system are designed and verified through mathematical proof and simulations.

• Journal of Power Electronics
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• v.9 no.5
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• pp.791-799
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• 2009

This paper presents a time-varying sinusoidal disturbance compensation method (based on an adaptive estimation scheme) for induction motor drives fed by a matrix converter. In previous disturbance accommodation methods, sinusoidal disturbances with unknown time-invariant frequencies have been considered. However, in the new method proposed here, disturbances with unknown time-varying frequencies are considered. The disturbances can be estimated by using a disturbance accommodating observer, and an additional control input is added to the induction machine drive. The stability analysis is carried out considering the disturbance estimation error and simulation results are shown to illustrate the performance of the proposed solution.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.2116-2124
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• 2018

Magnetic levitation system with the advantages of non-contact, no friction and no wear can satisfy the requirement of high precision and high speed positioning. In this paper, magnetic levitation positioning stage which mainly consists of planar coil and HALBACH permanent magnet array and its control and driving system are designed. Magnetic levitation system is a highly nonlinear and strongly coupled complex system and its control performance can be influenced by the uncertainty and external disturbance. So exact feedback linearization method is used to realize exact linearization and decoupling, and a strategy of sliding mode control based on disturbance observer is proposed to compensate the uncertainty and external disturbance. Detailed proofs of observer's convergence property and system stability are derived. Both the simulation and experiment results verify the effectiveness of sliding mode control algorithm based on disturbance observer.

• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.273-280
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• 2012

Most variable speed wind turbines have pitch control mechanisms and one of their objectives is to protect turbines when the wind speed is too high. By adjusting pitch angles of wind turbine, the inlet power and the torque developed by the turbine are regulated. In this paper, the difference between the real wind speed and its rated value is regarded as a disturbance, and a component called disturbance observer (DOB) is added to the pre-designed control loop. The additional DOB based controller estimates the disturbance and generates a compensating signal to suppress the effect of disturbance on the system. As a result, the stability and the performance of the closed loop system guaranteed by an outer-loop controller (designed for a nominal system without taking into account of disturbances) are approximately recovered in the steady state. Simulation results are presented to verify the performance of the proposed control scheme.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.4
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• pp.666-671
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• 2017

A disturbance-observer-based adaptive neural tracker design problem is investigated for a class of perturbed uncertain non-affine nonlinear systems with unknown control direction. A nonlinear disturbance observer (NDO) design methodology using neural networks is presented to construct a tracking control scheme with the attenuation effect of an external disturbance. Compared with previous control results using NDO for nonlinear systems in non-affine form, the major contribution of this paper is to design a NDO-based adaptive tracker without the sign information of the control coefficient. The stability of the closed-loop system is analyzed in the sense of Lyapunov stability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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• pp.104-110
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• 2015

The disturbance observer (DOB) controller has been widely used in various industrial applications since it is capable of achieving robust stability and disturbance rejection. In this paper, we study the effect of Q-filter on disturbance observer controller for Electro-Magnetic suspension (EMS) systems. We consider three Q-filters and analyze their effects on the robust stability against parameter uncertainties due to mass variation. Moreover, we investigate the influence of sensor noise for three Q-filters. According to our study, robust stability improves as the order of Q-filter decreases. On the other hand, the larger the order of Q-filter, the more the effect of sensor noise can be removed.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1676-1679
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• 2007

In control of the time delay systems, if the disturbance information can be estimated exactly, the ideal response for the disturbance can be achieved. Therefore, in this paper, a new adaptive disturbance observer for the time delay system control is proposed. The disturbance observer is designed and adaptive laws for adjusting the observer are proposed. The new Smith predictor controller to eliminate the effects of the disturbance can be achieved by adding an estimated disturbance to the Smith model. The improved performances of the proposed system and the adaptive disturbance observer are verified by computer simulation.