• Journal of Institute of Control, Robotics and Systems
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• v.17 no.7
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• pp.619-624
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• 2011

This paper presents a controller design method for a robust control problem with multiple constraints using genetic algorithms and LMI design method. A robust $H_{\infty}$ constraint with loop shaping and pole placement is used to address disturbance attenuation with error limits and desired transient specifications, in spite of the plant uncertainties and disturbances. In addition, a loop gain constraint is considered so as not to enlarge the loop gain unnecessarily. The robust $H_{\infty}$ constraint and pole placement constraint can be expressed in terms of two matrix inequalities and the loop gain constraint can be considered as an objective function so that genetic algorithms can be applied. Accordingly, a robust controller can be obtained by integrating genetic algorithms with LMI approach. The proposed controller design method is applied to a track-following system of an optical disk drive and is evaluated through simulation results.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.3
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• pp.9-16
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• 1996

LQ-servo is a robustness guaranteed multivariable controller design method based on the LQR structure to improve command following with output feedback. in this paper we introduce a weighting factor on the low frequency part of the state weighting matrix in the performance index in order to increase the low frequency gain of loop transfer function matrix T(s) in the loop shaping design method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.342-347
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• 1995

Loop shaping $H_{\infty}$control with normalized coprime factorization was applied to a servo-motor driven high-speed powitioning system. The high-gain controller was designed to attenuate the postion errors caused byfriction effects and extermal disturbances. The non-existence of limit cycle was analyzed, though there is actuator saturation. The designed $H_{\infty}$control system was experimently tested in a rotary index table. Results showed its effectiveness to improve postion accuracy with out any compensation scheme for friction, and robustness to model perturbation and external disturbances.ces.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.41-44
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• 2003

Generally, the frequency of set makes ICI and degrades OPDM system performance. Thus, we propose a pulse shaped OFDM to give robustness against the frequency offset. The proposed OFDM system uses pulse shaping with smooth shape, instead of rectangular pulse shape, to reduce the power of ICI. The proposed scheme always gives performance gain in comparing with the convention one, when the frequency offset exists. In addition, the smoother pulse shape is employed in the proposed system, the more performance gain is obtained.

• Journal of Power System Engineering
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• v.2 no.2
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• pp.67-72
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• 1998

To improve control performance, especially positioning speed, of a pneumatic positioning system, dynamic characteristics of a control valve should be considered. In case we design controller including dynamic characteristics of a control valve, it's not easy to design controller gain using simple state feedback because degree of a control system is increased. This study designed controller using loop shaping of $H_{\infty}$ control theory for a model composed of a pneumatic actuator and a control valve, and positioning experiment using this controller was performed. As a result, it was verified that the controller is useful for high speed positioning of a pneumatic positioning system.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.5
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• pp.443-449
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• 1997

LQ-servo design procedure introduced by Athans is a method using a partial states feedback and an output feedback in order to improve the poor performance robustness of the LQR as well as to maintain its stability robustness. Although the method guarantees good stability robustness, it is not effective in performance robustness as it does not match the singular value at low or high frequencies of the transfer matrix obtained by breaking at the plant output. This paper intends propose of a new method, using the limited behaviour of the control gain introduced by Kwakernaak and Sivan, in order to improve it does it refer to controlga introduced by kwakernaak or the new metho Anblguouls.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.16-23
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• 1990

In this paper, the shaped offset Cassegrain antenna with low sidelobe, low cross-polar level, and high efficiency is designed. The design data is presented for shaping scheme. The validity of radi-ation characteristics is accomplished by comparing the result of measurement with numerical calculation and design goal. Experimental results of designed antenna are in good agreement with design goal except efficiency.

• Journal of information and communication convergence engineering
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• v.2 no.1
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• pp.5-8
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• 2004

DS-COMA is now a matured multiple access technology that utilizes spreading codes for user separation. In this paper, we attempt to improve the performance of a multiuser DS-COMA system with a unique chip shaping code called Carrier Interferometry (CI) code. The CI codes exhibit an excellent correlation property that can be used in many applications. In DS-COMA with CI codes (CI/DS-COMA), the symbols are spread by a spreading code and then the chip signals are shaped using a CI code. Due to the correlation property of the CI code, a diversity gain from the shaped chip signals is achieved and the performance of DS-COMA is significantly improved. Comparison study demonstrates that the DS-COMA with CI outperforms the conventional DS-COMA system in multiuser environments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.454-463
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• 2000

A method is presented to alter the geometry of the conventional linearly shaped wire antenna for increasing its bandwidth. The synthesis is two-demensionally symmetric and is based on the minimization of frequency-dependence of the boresight far-field electric field intensity. The current distribution on the wire is calculated by Galerkin method using pulse functions. The shaping limitation for wide-band characteristics is still found because of standing waves due to reflected waves from antenna ends. The limitation overcome by a distribution of resistive loads near ends of wire. The antenna loaded resistively has flat characteristics satisfying a power gain of $6.5\pm1.1$dBi and VSWR of at most 2 over 10:1 bandwidth. The results are verified by comparing with similar results for the conventional linear V-dipole.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.3 s.118
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• pp.323-333
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• 2007

In this paper, a new MDAS-DR antenna structure designed to efficiently shape a flat-topped radiation pattern is proposed. The antenna structure is composed of a stacked micro-strip patch exciter and a multi-layered disk array structure(MDAS) surrounded by a dielectric ring. The MDAS, which was supplied by a stacked microstrip patch exciter with radiating power, can form a flat-topped radiation pattern in a far field by a mutual interaction with the surrounding dielectric ring. Therefore, the design parameters of the dielectric ring and the MDAS structure are important design parameters for shaping a flat-topped radiation pattern. The proposed antenna used twelve multi-layered disk array elements and a Teflon material with a dielectric constant of 2.05. An antenna operated at 10 GHz$(9.6\sim10.4\;GHz)$ was designed in order to verify the effectiveness of the proposed antenna structure. The commercial simulator of CST Microwave $Studio^{TM}$, which was adapted to a 3-D antenna structure analysis, was used for the simulation. The antenna breadboard was also fabricated and its electrical performance was measured in an anechoic antenna chamber. The measured results of the antenna breadboard with a flat-topped radiation pattern were found to be in good agreement with the simulated one. The MDAS-DR antenna gain measured at 10 GHz was 11.18 dBi, and the MDAS-DR antenna was capable of shaping a good flat-topped radiation pattern with a beam-width of about $40^{\circ}$, at least within a fractional bandwidth of 8.0 %.