• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
• /
• pp.501-504
• /
• 2003

This paper presents a new fractal coding scheme to find more optimal transformation by estimation of the optimal attractor. The conventional fractal coding schemes based on the collage theorem obtain the transformation to minimize the distance between an original image and its collage image. Heavy computation is why the schemes widely adopt the theorem. In other words, the optimal transformation can be obtained after the attractors of all the possible transformations are generated and then compared with an original image. It is clear that this process is not practical. Therefore, we introduce a sub-optimal scheme that provides better transformation than the conventional scheme, relieving the complexity problem in the optimal transformation. In a simple case, the optimal transformation can be obtained considering all the attractors and then our scheme is compared with the optimal. In general cases not to be able to find the optimal, our scheme is also evaluated and compared with the conventional schemes.

• 한국소음진동공학회논문집
• /
• 제14권2호
• /
• pp.157-163
• /
• 2004

Optimal transducer positions are important as much as the control algorithms and hardware performance in the active noise control system. This study is similar to the past researches on the optimal transducer locations but with a far field noise source having a plane wave characteristic and the noise coming through an opening such as a window in an enclosure. Optimization techniques are used to find sets of optimal loudspeaker positions from a larger possible loudspeaker positions. Loudspeakers are placed on the surface of opening at the wall and inside of the enclosure. Using the measured acoustic transfer impedances and numerical simulations with the optimization technique, optimal positions are identified and compared. When a small number of loudspeakers are used. loudspeaker positions on the opening near the center seems to be the best place, but when a larger number of loudspeakers are used it was difficult to find simple patterns in the optimal positions. With the optimally positioned loudspeakers, optimal microphone positions are also studied.

• 한국군사과학기술학회지
• /
• 제11권3호
• /
• pp.5-12
• /
• 2008

This paper presents the features of an impact angle constrained open-loop optimal trajectory which is given by a function of initial conditions and optimal guidance gains. Using missile motion described by linearized kinematic equations and a proper form of performance index, an inverse optimal problem is suggested to investigate the gains related to the performance index. The flight trajectory and time-to-go can be shaped in terms of the optimal guidance gains. The results are evaluated by 3-DOF simulation.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제23권4호
• /
• pp.351-365
• /
• 2019

This article presents a new approach for conformal flattening with optimal cone singularity. The algorithm here takes an optimal control for selecting optimal cones and uses the Ricci flow to force the flattening. This work is considered as a modification to the work of Soliman et al. [1] in the sense that they make use of the Yamabe equation for the flattening, which is an approximation of the Ricci flow. We present a numerical algorithm based on the optimal control with the mathematical background. Several numerical results validate that our method is optimal in total cone angle and usage of the Ricci flow ensures the conformal flattening while selecting optimal cones.

• 한국지능시스템학회논문지
• /
• 제6권2호
• /
• pp.111-119
• /
• 1996

In this paper, we propose time-optimal trajectory planning algorithms for cooperative multi-robot manipulators system considering optimal load distribution. Internal forces essentially effect on time optimal trajectory planning and if they are comitted, the time optimal scheme is not no longer true. Therefore, we try to find the internal force factors of cooperative robot manipulators system in a time-optimal aspect. In this approach, a specific generalized inverse is used and is fuzzified for the purpose. In this optimal method, the fuzzy logic concept is used and selected for diminishing computation time, for finding the load distribution factors.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 C
• /
• pp.915-917
• /
• 1998

Optimal routing of distribution networks can be attained by keeping the line power capacity limit to handle load requirements, acceptable voltage at customer loads, and the reliability indices such as SAIFI, SAIDI, CAIDI, and ASAI limits. This method is composed of optimal loss reduction and optimal reliability cost reduction. The former is solved relating to the conductor resistance of all alternative routes, and the latter is solved relating to the failure rate and duration of each alternative route. The routing considering optimal loss only and both optimal loss and optimal reliability cost are compared in this paper. The results showed that reliability cost should be considered as well as loss reduction to achieve the optimal routing in the distribution networks.

• Journal of Power Electronics
• /
• 제12권5호
• /
• pp.769-777
• /
• 2012

In this paper, a new development in the time optimal control theory in sliding mode control systems for multi-quadrant buck converters with a variable load is presented. In general, the closed-loop time optimal control system is applied to multi-quadrant buck converters for output regulation, so that an optimal switching surface is obtained. Moreover, an adjusted optimal sliding mode controller is suggested which adjusts the controller parameters to give an optimal switching surface. In addition, a description of the transient response of the closed-loop system is proposed and used to damp any output or input disturbances in minimum time. Numerical simulations and experimental results are employed to demonstrate that the output regulation time and transient performances of dc/dc converters using the proposed technique are improved effectively when compared to the classical sliding mode control method.

• Smart Structures and Systems
• /
• 제15권2호
• /
• pp.355-373
• /
• 2015

An optimal sensor placement (OSP) method based on structural subsection technique (SST) and model reduction technique was proposed for modal identification of truss structures, which was conducted using genetic algorithm (GA). The constraints of GA variables were determined by SST in advance. Subsequently, according to model reduction technique, the optimal group of master degrees of freedom and the optimal objective function value were obtained using GA in a case of the given number of sensors. Correspondingly, the optimal number of sensors was determined according to optimal objective function values in cases of the different number of sensors. The proposed method was applied on a scaled jacket offshore platform to get its optimal number of sensors and the corresponding optimal sensor layout. Then modal kinetic energy and modal assurance criterion were adopted to evaluate vibration energy and mode independence property. The experiment was also conducted to verify the effectiveness of the selected optimal sensor layout. The results showed that experimental modes agreed reasonably well with numerical results. Moreover the influence of the proposed method using different optimal algorithms and model reduction technique on optimal results was also compared. The results showed that the influence was very little.

• 한국조명전기설비학회지:조명전기설비
• /
• 제1권1호
• /
• pp.75-82
• /
• 1987

종래, 위상제어의 전력전자 회로는 전원에서 고주파분이 많이 포함되고 역율을 저하시키는 원인이 되었다. 그러므로, 본 연구에서는 이러한 영향을 개선시키기 위하여 Optimal PWM 방식을 제시하였다. Optimal PWM 콘버어터는 전원에서 실효 고주파분을 최소화하는 것이며, Optimal PWM 인버어터와 쌍대성이 있음을 알 수 있었다. Optimal PWM 콘버어터의 전류패턴은 Optimal PWM 인버어터의 전압패턴과 같은 스위칭패턴과 제어방법을 얻을 수 있었다. 이러한 PWM방식을 실현하기 위하여 고속 스위칭소자가 필요하게 되었다. 이전에는 강제 전류회로인 싸이리스터가 사용되었으나, 최근에 와서는 전류용 TR 또는 GTO 소자 등을 사용함으로써 이와같은 PWM 특성을 쉽게 실현할 수 있었다. 본 연구에서의 전원에서 실효 고주파 전류를 최소화하기 위한 제어방법, 회로 및 결과를 제시하였다.

• 한국강구조학회 논문집
• /
• 제21권4호
• /
• pp.361-373
• /
• 2009

유전자 알고리즘을 이용한 닐센아치교의 최적설계기법을 이 논문에서 제시하였다. 설계 매개변수로는 닐센아치교의 아치-라이즈비와 강중비에 대해서 최적화기법을 적용하여 각각의 거동을 분석하고, 적정성을 평가하여 최적의 매개변수 값을 결정하였다. 매개변수의 결정은 구조물의 안전성과 사용성 그리고 경제성에 중요한 설계인자로서 정형화가 요구된다. 이를 위해 최적화 기법으로 전역 최적해 탐색능력이 우수한 유전자 알고리즘을 사용하였으며, 설계 목적함수로는 구조물의 총 중량을 사용하였고, 제약조건으로는 변위, 응력, 시공성 제약조건을 두었다. 구조해석은 미소변위이론에 의한 탄성해석을 수행하여 유전자 알고리즘과 조합하여 병렬연산으로 수행시간을 단축시켰다. 이 연구에서 개발된 최적설계기법을 사용하여 최적의 아치-라이즈비와 강중비, 최적설계영역을 제시 하였으며 실무에 적용할 수 있도록 하였다.