• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.1
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• pp.57-66
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• 2012

This paper proposes a performance improvement of grid-connected inverter system using sliding-mode based direct power control with a variable gain. The proposed control method determine variable gain of PI controller by using modeling at direct power control (DPC) applied to space vector modulation method. Also, this method use sliding-mode control to maintain excellent dynamic response of character of direct power control (DPC). The validity of the proposed algorithm are verified by simulations and experiments.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.11
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• pp.763-770
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• 2000

The speed and position information of the rotor are required in the speed control of SRM(Switched Reluctance Motors). This information is generally provided by shaft encoder or resolver. It is weak in the dusty, high temperature, and EMI environment. Consequntly, much attention has been given to SRM control for eliminationating the position and speed sensors. In this paper, a new estimation algorithm for the rotor position and speed for SRM drives is described. The algorithm is implemented by the sliding mode observer. The stability and robustness of the sliding observer for the parameter variations of the SRM are proved by variable structure control theory. Speed control of the SRM is accomplished by the estimated speed and position. Experiment results verify that the mode observer is able to estimate the speed and position well.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.843-847
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• 2011

In this note, a proof of Utkin's theorem is presented for the SI(Single Input) uncertain integral linear case. The invariance theorem with respect to the two transformation methods so called the two diagonalization methods are proved clearly and comparatively for SI uncertain integral linear systems. With respect to the sliding surface transformation, the equation of the sliding mode, the sliding surface is invariant. Both the applied control inputs have the same gains. By means of the two transformation methods the same results can be obtained. Through an illustrative example and simulation study, the usefulness of the main results is verified.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.3
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• pp.208-213
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• 2013

The problem of finding control laws for underactuated systems has attracted growing attention since these systems are characterized by the fact that they have fewer actuators than the degrees of freedom to be controlled. A sliding mode control based on the theory of variable structure systems is a robust methodology to control nonlinear systems. In this paper, a sliding mode control with integral sliding function is proposed and asymptotical stability is proved in the Lyapunov's sense for underactuated systems. In order to verify the effectiveness of the proposed control, computer simulations for an acrobot, which is a representative underactuated system, are performed. Using Mathworks' Simulink/Simscape, the acrobot dynamics is implemented and the proposed control is composed. Simulations demonstrate the effectiveness and usefulness of the proposed control.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.3
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• pp.30-39
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• 2011

In this note, a systematic design of a new robust nonlinear continuous variable structure control system(VSCS) based on the modified state dependent nonlinear form is presented for the control of uncertain affine nonlinear systems with mismatched uncertainties and matched disturbance. After an affine uncertain nonlinear system is represented in the form of state dependent nonlinear system, a systematic design of a new robust nonlinear VSCS is presented. The uncertainty of the nonlinear system function is separated into the tow parts, i.e., state dependent term and state independent term for extension of target plants. To be linear in the closed loop resultant dynamics and in order to easily satisfy the existence condition of the sliding mode, the transformed linear sliding surface is applied. A corresponding control input is proposed to satisfy the closed loop exponential stability and the existence condition of the sliding mode on the linear transformed sliding surface, which will be investigated in Theorem 1. For practical application, the discontinuity of the control input as the inherent property of the VSS is improved dramatically. Through a design example and simulation studies, the usefulness of the proposed controller is verified.

• Korean Journal of Remote Sensing
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• v.22 no.6
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• pp.601-612
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• 2006

This study proposes RAG (Region Adjancency Graph)-based image segmentation for large imagery in remote sensing. The proposed algorithm uses CN-chain linking for computational efficiency and multi-window operation of sliding structure for memory efficiency. Region-merging due to RAG is a process to find an edge of the best merge and update the graph according to the merge. The CN-chain linking constructs a chain of the closest neighbors and finds the edge for merging two adjacent regions. It makes the computation time increase as much as an exact multiple in the increasement of image size. An RNV (Regional Neighbor Vector) is used to update the RAG according to the change in image configuration due to merging at each step. The analysis of large images requires an enormous amount of computational memory. The proposed sliding multi-window operation with horizontal structure considerably the memory capacity required for the analysis and then make it possible to apply the RAG-based segmentation for very large images. In this study, the proposed algorithm has been extensively evaluated using simulated images and the results have shown its potentiality for the application of remotely-sensed imagery.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.4
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• pp.55-61
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• 1995

Variable structure control (VSC) can be used for the control of power plants required stability and robustness such as elevator control. It has no overshoot and is insensitive to parameter variations and disturbances in the sliding mode where the system structure is changed with the sliding surface in the center. But in the real system, VSC has a high frequency chattering which has a bad influence upon the control system proformances. In this paper, to alleviate the high frequency chattering, a binary controller (BC) with inertial type external loop is implemented by DSP and applied to position control of brushless DC motor. Binary controller has external loop to generate the continuous control input with the flexible variation of primary loop gain. Thus it has the property of chattering alleviation in addition to advantages of the conventional variable structure control.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.585-587
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• 1994

The chattering phenominon is the one of the problems on Variable Structure Controller(VSC). To alleviate this problem, Modified Variable Structure Controller(MVSC) with sliding sector is presented in this paper. This controller is adopted to the position drive system of brushless dc motor. For the simplification of hardware, the current controller also uses the sliding mode control method. Computer simulations are presented to show chattering alleviation of the proposed control scheme.

• Journal of Electrical Engineering and information Science
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• v.3 no.1
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• pp.58-66
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• 1998

A continuous, accurate, and robust variable structure tracking controller(CVSTC) is designed for brushless direct drive servo motors(BLDDSM). Although conventional variable structure controls can give the desired tracking performances, there exists an inevitable chattering problems in control input which is undesirable for direct drive systems. With the presented algorithm, not only the chattering problems are removed by using the efficient compensation of the disturbance observer, but also the prescribed tracking trajectory can be obtained using the sliding dynamics when an initial of the desired trajcetory is different from that of a BLDDSM. The design of the sliding mode tracking controller for the prescribed, accurate, and robust tracking performance without the chattering problem is given based on the results of the detailed stability analysis. The usefulness of the suggested algorithm is demonstrated through the computer simulation for a BLDDSM under load variations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1498-1507
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• 1996

This paper presents a robust control of a smart flexible structure featured by a piezofilm actuator characterizing its light weght and quick response time. A mathematical governing equation for the proposed structure is derived by employing Hamilton's principle and a state space control model is subsequentrly obtained through modal analysis. Uncertain system parameters such as frequency variation are included in the control model. A sliding mode control theroy thich has inherent robustness to systme uncertainties is adopted to design a tracking controller for the peizofilm actuator. Using the output informaiton from the tip deflection sensor, a full-order observer is constructed ot estimate state variables for the system. Tracking performances for desired trajectories of sinusoidal amd step functions are evaluated by undertaking both simulation and experimental works.