• Journal of Magnetics
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• v.6 no.3
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• pp.101-107
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• 2001

A model to describe the effect of stator slotting in the airgap region of a linear brushless permanent magnet motor (LBLPMM) is proposed for analytical prediction of magnetic field distribution. It is a two-dimensional model based on superposition of the effect of stator slotting and main field due to permanent magnet (PM) without stator slotting. The effect of stator slotting is expressed in form of a generalized equation, which is obtained by numerical analysis and is a function of motor geometric parameters, so the proposed model effectively accounts for the effect of stator slotting in the airgap field distribution according to change of motor geometry or relative motion of stator and armature. Results of prediction from the proposed model are compared with corresponding finite element analysis.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.31-35
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• 2019

Human beings have been fascinated by the applicability of the medium of photography since the device was first introduced in the thirteenth century to acquire images by attempting primitive and rudimentary approaches. In the 21st century, it has been developed as a wide range of technology that enables not only the application of artistic expression as a method of replacing the human-hand-painted screen but also the planar recording form in the format of video or image. It is more effective to use the information extracted from the image data rather than to use a randomly given file name in order to provide a variety of services in the offline or online system. When extracting an identifier from a region of an image, high cost cannot be avoided. This paper discusses the image entropy-based approach and proposes a linear methodology to measure the image entropy in an effort to devise a solution to this method.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.154-158
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• 2015

We experimentally demonstrated a novel wavelength-swept laser using a cascaded Raman gain around 1310 nm. A 1064/1310 wavelength division multiplexing (WDM) coupler and coupled fiber Bragg gratings mirrors at 1064, 1117, 1175, 1240 nm are effectively used to increase the power efficiency in a laser ring cavity with highly non-linear fiber (HNLF) of 2 km. Linear wavelength sweeping is demonstrated with the 100 Hz triangular driving signal to fiber Fabry-Perot tunable filter (FFP-TF) around the 1310 nm region. The measured sweeping range and output power were 27 nm and 2.1 mW, respectively, which are suitable for optical coherence tomography (OCT) imaging.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.4
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• pp.279-283
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• 2005

This paper deals with the design of a low-order H/sub ∞/ controller by using an iterative linear matrix inequality (LMI) method. The low-order H/sub ∞/ controller is represented in terms of LMIs with a rank condition. To solve the non-convex rank-constrained LMI problem, the recently developed penalty function method is applied. With an increasing sequence of the penalty parameter, the solution of the penalized optimization problem moves towards the feasible region of the original non-convex problem. Numerical experiments showed the effectiveness of the proposed algorithm.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.873-876
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• 1993

A fuzzy controller designed by mini-max-gravity(MMG) method is essentially nonlinear with respect to the controller's input and output relationship, and stability analysis is thus needed to construct a stable control system. This paper deals with a design method of a position-type MMG fuzzy controller stable in a sense of Lyapunov when considered is a single-input-single-output linear, stable plant. We first introduce a method to construct a Laypunov function by using an eigen-value of A matrix of the linear, stable plant dynamics and then we derive an asymtotic stability condition in terms of scale factors for fuzzy state variables and controller gain. The stability condition is found reasonably practical through comparing the theoretical stability region with that obtained from simulations.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.496-501
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• 2003

Reynolds averaged Wavier-Stokes simulations based on the Reynolds stress model was performed to investigated the effect of inlet flow angle on the distributions of the Reynolds stress tensor inside tip leakage vortex of a linear compressor cascade. Two different inlet flow angles ${\beta}=29.3^{\circ}$(design condition) and $36.5^{\circ}$(off-design condition) were considered. Stress tensor analysis, which transforms the Reynolds stress into the principal direction, was applied to show an anisotropy of the normal stresses. Whereas the anisotropy was highest in the region where the tip leakage vortex collides the suction side of the blade and tip leakage flow enters between blade tip of the pressure side and the endwall, it had the lowest value at the center of tip leakage vortex. It was also found that the magnitude of maximum shear stress at design condition was greater than that of off-design condition.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.11
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• pp.905-912
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• 1989

An adaptive control scheme is presented for uncertain systems whose uncertainties are upper-bounded by a linear combination of unknown constants and known continuous functions. The state of the closed-loop system is proven to be ultimately bounded. The proposed method modifies the method of Corless and Leitmann in the following two respects. First, the linear region of the saturation function in controller is fixed. Second, the intergration from in parameter estimator is replaced by a low pass filter form. These modifications prevent performance degradation and destabilization of the control system more effectively. The norm of the system states can be made sufficiently small by an appropriate choice of design parameters in the control law. The applicability of the proposed scheme is demonstrated in the position control of a simple pendulum via simulation.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.3
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• pp.108-113
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• 2004

This paper presents methods to improve performance of the power supply system in a NASA deep space explorer. In the Stirling engine driven reciprocating Brushless DC (BLDC) generator, the accurate position information of the prime mover is important to diagnose the performance of the engine and prevent distortion of the output power. Since sensors to detect the position are fragile and unreliable, and conventional sensorless techniques have drawbacks in the low speed region, a novel sensorless position detection technique for the prime mover has been proposed and verified. Another major issue of the generator for the spacecraft is power density maximization. The mass of the power system is important to the mass of the satellite. Therefore, the components of the spacecraft should be lightweight. Conventional rectification methods cannot achieve the maximum power possible due to non-optimal current waveforms. The optimal current waveform for maximizing power density and minimizing machine size and weight in a nonsinusoidal power supply system has been derived, incorporated in a control system, and verified by simulation work.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.11
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• pp.33-35
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• 1993

A new low-power, high-order optimization scheme to design surface gradient coils (SGC) is proposed for magnetic resonance imaging (MRI). Although previous SGCs have been designed and constructed just to get strong linear gradients, this paper proposes more systematic ways of SGC design by minimizing electrical power consumption in the gradient coil and by removing unnecessary high-order field distortions in the imaging region. By assuming continuous current flow on the coil surface which may be or may not be planar, power consumption in the coil is minimized. According to the simulation results, the SGC designed by using the proposed scheme seems to produce much more uniform linear gradient field using less electrical power compared to the previously proposed SGCs.

• Proceedings of the KAIS Fall Conference
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• 2010.05a
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• pp.277-280
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• 2010

LSP(Line Spectrum Pairs) Parameter is used for speech analysis in vocoders or recognizers since it has advantages of constant spectrum sensitivity, low spectrum distortion and easy linear interpolation. However the method of transforming LPC(Linear Predictive Coding) into LSP is so complex that it takes much time to compute. Among conventional methods, the real root method is considerably simpler than others, but nevertheless, it still suffers from its indeterministic computation time because the root searching is processed sequentially in frequency region. We suggest a method of reducing the LSP transformation time using voice characteristics.