• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.463-468
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• 1992

In this paper, discrete-time H$_{\infty}$ controller design in .delta.- domaion using Normalized Coprime Factor plant description is proposed and the loop-shaping method developed by Mcfalane[2], which is known to be very simple and systematic method, is adopted here in H$_{\infty}$ controller design. In particular, we show that .delta.- H$_{\infty}$ controller proposed here is a unified form for the continuous and discrete-time cases.es.

• 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.

• Journal of Advanced Navigation Technology
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• v.20 no.3
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• pp.258-264
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• 2016

In this paper, we propose a computationally efficient direction of arrival (DoA) estimation algorithm based on propagator method with non-uniform array. While the co-prime array techniques can improve the resolution of DoA, they generally lead to high computational complexity as the length of the coarray aperture. To reduce the complexity we use the propagator method that does not require singular value decomposition (SVD). Through simulations, we compare MUSIC with uniform lineary array, propagator method with uniform linear array, MUSIC with co-prime array, and the proposed scheme and observe that the performance of the proposed scheme is significantly better than MUSIC or propagator method with uniform linear array while it is slightly worse than computationally much more expensive co-prime array MUSIC scheme.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.486-489
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• 2002

This paper proposes a tabu search (TS) algorithm to optimal weight selection in design of robust H$_{\infty}$ power system stabilize. (PSS), In H$_{\infty}$ control design, the weight selection and the representation of system uncertainties are the major difficulties. To cope with these problems, TS is employed to automatically search for the optimal weights. On the other hand, the normalized coprime factorization (NCF) is used. The H$_{\infty}$ controller can be directly developed without ${\gamma}$-iteration. Also, the pole-zero cancellation phenomena are prevented. The performance and robustness of the proposed PSS under different loading conditions are investigated in comparison with a robust tuned PSS by examining the case of a single machine infinite bus (SMIB) system. The simulation results illustrate the effectiveness and robustness of the proposed PSS.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.5
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• pp.17-24
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• 1996

In this paper, we present a robust performance improvement method for the NLCF(normalized left coprime factor) uncertain structure using loop shaping and the structure singular value. For this, we select weighting functions for a loop shaping considering condition numer, and transform the NLCF uncertain structure into the 4-block structure. However, we can't get a good performance on account of the restriction of weighting functions. To cope with this, we motivate the use of structured singular vlaue in the robust performance improvement procedure. After all, the robust performance improvement can be obtained by a factor W$_{a}$ and a scaling factor of D-K iteration.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.6
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• pp.425-434
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• 2003

The disturbance observer(DOB) has been widely used in high speed and high precision motion control applications and the characteristics of DOB have been investigated in depth. Though most of DOB's have been implemented as the discrete-time form in digital devices, we are still short of the researches on discrete-time DOB (DDOB) in spite of rich references on continuous-time DOB. In this paper, we discuss about the disturbance rejection property and measurement noise effect of discrete-time DOB. Especially, we will focus on revealing the role of sampling time in designing the discrete-time DOB and show the validity of analysis through simulations and experiments for optical disk drive systems.

• Journal of the Korean Mathematical Society
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• v.48 no.1
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• pp.191-205
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• 2011

It is well known that for a Krull domain R, the divisor class group of R is a torsion group if and only if every subintersection of R is a ring of quotients. Thus a natural question is that under what conditions, for a non-Krull domain R, every (t-)subintersection (resp., t-linked overring) of R is a ring of quotients or every (t-)subintersection (resp., t-linked overring) of R is at. To address this question, we introduce the notions of *-compact packedness and *-coprime packedness of (an ideal of) an integral domain R for a star operation * of finite character, mainly t or w. We also investigate the t-theoretic analogues of related results in the literature.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.569-572
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• 1996

Explicit state-space formulate for an H$_{.inf}$ based two-degrees-of-freedom robust controller are derived in discrete-time. The controller provides robust stability against coprime factor uncertainty, and a degree of robust performance in the sense of making the closed-loop system match a prespecified reference model. It is shown that the controller consists of a plant observer, the chosen reference model, and a generalized state feedback law associated with the plant and model states. The controller structure is shown to be relatively simple and thus may reduce the computational load on the digital control processor.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.943-946
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• 1988

A simple method is proposed for determining the frequency response function G(j.omega.) of a system using a pair of characteristic M-sequences (maximum length linear feed back shift register sequence). When a characteristic M-sequence is sampled with q$_{1}$ and q$_{2}$ both of which are coprime with N, where N is the period of the M-sequence, the obtained pair of sequences have conjugate complex frequency spectrum. Making use of this fact, two charcteristic M-sequences having conjugate complex frequency spectrum are applied to a system to be measured. Since the magnitude of spectrium of M-sequence is known, the gain of G(j.omega.) is directly obtained from the Fourier transform of the system output. The phase of G(j.omega.) is obtained simply by taking the average of the two phases of output spectrum.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.456-460
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• 1996

A nonlinear control scheme for preventing limit cycle due to the nonlinearity of themulti-step bang-bang actuator in mechanical position control systems is proposed. A linearized model, SIDF, fora multi-step bang-bang actuator is introduced to compensate the nonlinearity of the multi-step bang-bang actuator. Using that model, a $H_{\infty}$robust controller for position control systms with a bang-bang actuator is proposed by loop shaping tecniques with normalized coprime factorization stabilization to address the robustness. The proposed scheme needs a smaller deadband as a result of compensating the nonlinearity of the bang-bang actuator. A single-axis servo system is served in order to verify the proposed control scheme experimentally. Experimental results show that the controller can satisfy the special intersts, silent contact switching of the actuator.r.