• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.165-168
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• 2006

Exponential smoothing methods do not adapt well to unexpected changes in underlying process. Over the past few decades a number of adaptive smoothing models have been proposed which allow for the continuous adjustment of the smoothing constant value in order to provide a much earlier detection of unexpected changes. However, most of previous studies presented ad hoc procedure of adaptive forecasting without any theoretical background. In this paper, we propose a detection-adaptation procedure applied to simple and Holt's linear method. We derive level and slope change detection statistics based on Bayesian statistical theory and present distribution of the statistics by simulation method. The proposed procedure is compared with previous adaptive forecasting models using simulated data and economic time series data.

• 한국산업융합학회 논문집
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• 제6권4호
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• pp.379-386
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• 2003

The goal of this research is to develop a Heel/Side Laster and control GUI(Graphic User Interface) for adaptive manufacturing. For this purpose, we have analyzed the working sequences of heel/side laster, and developed a control program that will facilitate the machineries with functions that are suitable for adaptive manufacturing. We also made it possible to modify the gluing path with simple manipulation of CAD data. By providing a user-friendly GUI, we made it possible for unskilled workers use the system without difficulty. In addition, we have developed a flexible environment where the already available CAD data can be modified and saved with ease. Automatic feeding and path control algorithms for thermoplastic cement were also implemented. By using the Heel/Side Laster for adaptive manufacturing, we are able to achieve increased productivity and work efficiency while improving the quality of the product with self-diagnosis and fine adjustment function.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1060-1062
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• 1996

This paper presents a discrete adaptive observer for MIMO system of an IM model in DQ reference model. The IM model in the stationary frame is discretized and it is transformed into the canonical observer form. The unknown parameter is choosen as rotor speed. The adaptive law for parameter adjustment is obtained as a set of recursive equations which are derived by utilizing an exponentially weighted normalized least-square method. The proposed adaptive observer converges rapidly and is also shown to track time-varying plant parameter quickly. Its effectiveness has been demonstrated by computer simulation.

• Journal of Advanced Marine Engineering and Technology
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• 제30권7호
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• pp.791-799
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• 2006

The aim of this paper is to design an adaptive speed control system of a marine diesel engine by fusion of hard computing based proportional integral derivative (PID) control and soft computing based fuzzy control methods. The model of a marine diesel engine is considered as a typical non oscillatory second order system. When its model and the actual marine diesel engine ate not matched, it is hard to control the speed of the marine diesel engine. Therefore, this paper proposes two methods in order to obtain the speed control characteristics of a marine diesel engine. One is an efficient method to determine the PID control parameters of the nominal model of a marine diesel engine. Second is a reference adaptive speed control method that uses a fuzzy controller and derivative operator for tracking the nominal model of the marine diesel engine. It was found that the proposed PID parameters adjustment method is better than the Ziegler & Nichols' method, and that a model reference adaptive control is superior to using only PID controller. The improved control method proposed here, could be applied to other systems when a model of a system does not match the actual system.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제14권2호
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• pp.191-195
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• 2008

본 논문은 IEEE 802.11e EDCA의 성능 향상을 위해서 클래스 트래픽에 기반하여 각 클래스의 경쟁 윈도우의 크기를 동적으로 조절하는 방안을 제안한다. IEEE 802.11e EDCA는 IEEE 802.11 DCF와는 달리 서비스 차별화를 위해 네 개의 클래스 AC마다 고정된 최소 경쟁 윈도우 크기인 CWmin 값과 최대 경쟁 윈도우 크기인 CWmax 값을 적용한다. 트래픽의 특성별로 나뉜 AC의 고정된 파라미터 값은 각 AC간의 차별화를 보장하지만 네트워크 환경이 혼잡할 경우 충돌 발생 확률을 높인다. 이를 해결하기 위해 채널과 네트워크 상태를 고려하여 일정한 주기마다 계산된 충돌 확률로 CWmin 값을 조절하는 CWminAS(CWmin Adaptation Scheme)가 제안되었다. 그러나 이 방식은 AC별 다른 파라미터 값으로 인해 발생되는 각 AC의 충돌 확률을 고려하지 않았다. 이러한 문제를 해결하기 위해 본 논문에서는 AC별 다른 파라미터 값으로 인해 발생되는 각 AC의 충돌 확률을 계산하고, CWmin 값을 조절하는 ACATICT(Adaptive Contention-window Adjustment Technique based on Individual Class Traffic) scheme을 제안한다. 실험 결과 ACATICT가 CWminAS보다 효율이 최대 약 10% 향상되었다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.563-569
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• 2015

For some low-frequency applications such as power-related circuits, NEM relays have been known to show better performance than MOSFETs. For example, in a step-down charge pump circuit, the NEM relays showed much smaller layout area and better energy efficiency than MOSFETs. However, severe process variations of NEM relays hinder them from being widely used in various low-frequency applications. To mitigate the process-variation problems of NEM relays, in this paper, a new NEM-relay charge pump circuit with the self-adjustment is proposed. By self-adjusting a pulse amplitude voltage according to process variations, the power consumption can be saved by 4.6%, compared to the conventional scheme without the self-adjustment. This power saving can also be helpful in improving the power efficiency of the proposed scheme. From the circuit simulation of NEM-relay charge pump circuit, the efficiency of the proposed scheme is improved better by 4.1% than the conventional.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.19-22
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• 2004

This paper implemented 2.14GHz band Adaptive Hybrid Doherty (AHD) amplifier, as well as, wished to improve the high power characteristics and efficiency by composing bias adjustment circuit with LDMOS. Finally, through CAE, confirmed that AHD amplifier have superior performance than hybrid balanced amplifier. Superior characteristics of AHD amplifier is expected to affect immensely in amplifier field hereafter.

• 한국정밀공학회지
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• 제3권1호
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• pp.29-39
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• 1986

An adaptive controller which is robust to the unknown load disturbance is developed for electro-hydraulic speed control systems. Since the load disturbance degrades the performance of the controller such as a steady state error and rise time in the conventional control system, appropriate adjustment of the controller is necessary in order to obtain the desired performances. The adaptation mechanism was designed to tune the feedforward gain, based upon minimization of ITAE (integral of time-multiplied absolute error) performance. The unknown load distrubance was identified by using an analog computer from the relationship between the velocity of the hydraulic motor and the load pressure. To evaluate the performance of the controller a series of simulations and experiments were conducted for various load conditions. Both results show that the proposed adaptive controller shows abetter performance than the conventional controller in terms of the steady state error and rise time.

• 대한교통학회지
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• 제14권2호
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• pp.89-118
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• 1996

The development and implementation of a real-time, traffic adaptive control scheme based on fuzzy logic through Video Image Detector systems (VIDs) is presented. Through VIDs based image processing, fuzzy logic can be used for a real-time traffic adaptive signal control scheme. Fuzzy control logic allows linguistic and inexact traffic data to be manipulated as a useful tool in designing signal timing plans. The fuzzy logic has the ability to comprehend linguistic instructions and to generate control strategy based on a priori verbal communication. The implementation of fuzzy logic controller for a traffic network is introduced. Comparisons are made between implementations of the fuzzy logic controller and the actuated controller in an isolated intersection. The results obtained from the application of the fuzzy logic controller are also compared with those corresponding to a pretimed controller for the coordinated intersections. Simulation results from the comparisons indicate the performance of the system is between under the fuzzy logic controller. Integration of the aforementioned schemes into and ATMS framework will lead to real-time adjustment of the traffic control signals, resulting in significant reduction in traffic congestion.

• 대한기계학회논문집
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• 제14권3호
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• pp.513-525
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• 1990

본 연구에서는 ARSC의 이론적인 전개에 대해서 주로 설명하고자 한다. 제2 장에서는 ARSC의 구조를 자세히 기술하며, 제3장에 ARSC를 컴퓨터에 이식하기 위한 알 고리즘을 요약하여 제시한다. 또한, ARSC알고리즘이 총체적으로(globally) 수렴하며 안정하다는 이론적 증명에 대하여 제4장에서 언급하며, 마지막으로 제5장에 실시간 시 뮬레이션을 통하여 ARSC의 간단한 적용실례를 들었다. 실제로 본 ARSC는 엔드밀링의 절삭력 적응제어에 적용되었는데, 그 연구결과는 별도로 발표할 예정이다.