• Smart Structures and Systems
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• 제6권7호
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• pp.767-792
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• 2010

In this paper, the optimal design of vibration control system for smart structures has been investigated semi-analytically via the optimization of geometric parameters like the placements and sizes of piezoelectric sensors and actuators (S/As) bonded on the structures. The criterion based on the maximization of energy dissipation was adopted for the optimization of the control system. Based on the sensing and actuating equations, the total energy stored in the system which is used as the objective function was analytically derived with design variables explicitly presented. Two cases of single and combined vibration modes were addressed for a simply supported beam and a simply supported cylindrical shell. For single vibration mode, the optimal distributions of the piezoelectric S/As could be obtained analytically. However, the Sequential Quadratic Programming (SQP) method has to be employed to solve those which violated the prescribed constraints and to solve the case of combined vibration modes. The results of three examples, which include a simply supported beam, a simply supported cylindrical shell and a simply supported plate, showed good agreement with those obtained by the Genetic Algorithm (GA) method. Moreover, in comparison with the GA method, the proposed method is more effective in obtaining better optimization results and is much more efficient in terms of computation time.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2221-2229
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• 2022

In this research, for improving the measurement performance of Prompt Gamma-ray Neutron Activation Analysis (PGNAA) set-up, a new optimization method for set-up design was proposed and investigated. At first, the calculation method for Signal-to-Noise Ratio (SNR) was proposed. Since the SNR could be calculated and quantified accurately, the SNR was chosen as the evaluation parameter in the new optimization method. For discussing the feasibility of the SNR optimization method, two kinds of PGNAA set-ups were designed in the MCNP code, based on the SNR optimization method and the previous signal optimization method, respectively. Meanwhile, the single element spectra analysis method was proposed, and the analysis effect of single element spectra as well as element sensitivity were used for comparing the measurement performance. Since the simulation results showed the better measurement performance of set-up designed by SNR optimization method, the experimental set-ups were built for the further testing, finally demonstrating the feasibility of the SNR optimization method for PGNAA setup design.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1999년도 추계학술대회 논문집
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• pp.63-69
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• 1999

The research trend of the simulation optimization has been focused on exploring continuous decision variables. Yet, the research in discrete decision variable area has not been fully studied. A new research trend for optimizing discrete decision variables ha just appeared recently. This study, therefore, deals with a discrete simulation method to get the system evaluation criteria required for designing a complex probabilistic discrete event system and to search the effective and reliable alternatives to satisfy the objective values of the given system through a on-line, single run with the short time period. Finding the alternative, we construct an algorithm which changes values of decision variables and a design alternative by using the stopping algorithm which ends the simulation in a steady state of system. To avoid the loss of data while analyzing the acquired design alternative in the steady state, we provide background for estimation of an auto-regressive model and mean and confidence interval for evaluating correctly the objective function obtained by small amount of output data through simulation with the short time period. In numerical experiment we applied the proposed algorithm to (s, S) inventory system problem with varying Δt value. In case of the (s, S) inventory system, we obtained good design alternative when Δt value is larger than 100.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.140-145
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• 1992

This paper presents a decentralized model reference adaptive control scheme for an interconnected linear system composed of a number of single-input single-output subsystems in which outgoing interactions pass through the measurement channel and are subjected to bounded external disturbances. The scheme can treat the unknown strength of interactions as well as uncertainties in subsystem dynamics, and allows for the case when the relative degree of each decoupled subsystem does not exceed two.

• 한국전자통신학회논문지
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• 제12권5호
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• pp.851-858
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• 2017

본 연구에서는 SPWM 구동방식의 단상 풀 브리지 인버터의 전압제어계를 설계하였다. 전압제어계는 단상 풀-브리지 인버터, 출력전압과 기준전압의 오차를 선형적으로 보상하기 위한 PI 제어기, 제어기 신호로부터 SPWM 방식을 이용하여 게이트 신호를 발생시키기 위한 PWM 구동회로, 인버터 출력 전압 파형을 정현 파형으로 필터링하기 위한 LC 필터로 구성하였다. 끝으로, EMTP-RV를 이용하여 PWM 구동방식을 기반으로 하는 단상 풀-브리지 인버터의 전압 제어계를 모델링하였고 수개의 기준전압에 대한 시뮬레이션 연구를 통해 출력전압이 정확하게 기준전압을 수렴하는 것을 확인함으로서 제어계 설계의 유효성을 확인할 수 있었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 추계학술대회 논문집
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• pp.63-64
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• 2016

This paper deal with single module design of 13.2kVrms/10kVA solid state transformers exchanging conventional transformer. We can design compact hardware system to reduce size and get higher switching frequency by using SiC devices. As a result by comparing simulation results with experiment result, it is verified.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1388-1395
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• 2017

The Helically coiled tube Once-Through Steam Generator (H-OTSG) is a key piece of equipment for compact small reactors. The present study developed and verified a thermal-hydraulic design and performance analysis computer code for a countercurrent H-OTSG installed in a small pressurized water reactor. The H-OTSG is represented by one characteristic tube in the model. The secondary side of the H-OTSG is divided into single-phase liquid region, nucleate boiling region, postdryout region, and single-phase vapor region. Different heat transfer correlations and pressure drop correlations are reviewed and applied. To benchmark the developed physical models and the computer code, H-OTSGs developed in Marine Reactor X and System-integrated Modular Advanced ReacTor are simulated by the code, and the results are compared with the design data. The overall characteristics of heat transfer area, temperature distributions, and pressure drops calculated by the code showed general agreement with the published data. The thermal-hydraulic characteristics of a typical countercurrent H-OTSG are analyzed. It is demonstrated that the code can be utilized for design and performance analysis of an H-OTSG.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 B
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• pp.528-530
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• 1999

This paper addresses the analysis and design of fuzzy control systems for a class of complex single input single output nonlinear systems. Firstly, the nonlinear system is represented by well-known Takagai-Sugeno (TS) fuzzy model and the global controller is constructed by compensating each linear model in the rule of TS fuzzy model. The design of conventional TS fuzzy-model-based controller usually is composed of two processes. One is to determine static state feedback gain of each local model and the other is to validate the stability of the designed fuzzy controller. In this paper, we propose an alternative of the design of TS fuzzy-model-based controller. The design scheme is based on the extension of conventional optimal control theory to the design of TS fuzzy-model-based controller. By using the proposed method the design and stability analysis of the TS fuzzy model-based controller is reduced to the problem of finding the solution of a set of algebraic Riccati equations. And we use the recently developed interior point method to find the solution of AREs, where AREs are recast as the LMI formulation. One simulation example is given to show the effectiveness and feasibility of the proposed fuzzy controller design method.

• International Journal of Automotive Technology
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• 제8권6호
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• pp.771-780
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• 2007

In recent studies, various types of multi mode electric variable transmissions of hybrid electric vehicles have been proposed. Multi mode electric variable transmission consists of two or more different types of planetary gear hybrid powertrain system(PGHP), which can change its power flow type by means of clutches for improving transmission efficiencies. Generally, the power flows can be classified into three different types such as input split, output split and compound split. In this study, we analyzed power transmission characteristics of the possible six input split systems, and found the suitable system for single or multi mode hybrid powertrain. The input split system used in PRIUS is identified as a best system for single mode, and moreover we identified some suitable systems for dual mode.

• 한국통신학회논문지
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• 제41권11호
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• pp.1380-1386
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• 2016

본 논문에서는 BPSK변조를 사용하는 OFDM(Orthogonal Frequency Division Multiplexing)기반의 시스템에서 2 branch로 나눈 후에 DCT(Discrete Cosine Transform)를 사용하고 DHT(Discrete Hilbert Transform)와 복소수를 이용하여 스펙트럼을 변화시켜 SSB(Singe Side Band) 전송과 같은 효과를 내는 시스템 모델을 제시하고 성능을 평가한다. 또한 제안하는 시스템은 한 정보신호를 SSB전송과 같이 절반의 스펙트럼으로 송신을 할 뿐만 아니라 전체의 스펙트럼을 양측파대라 할 때 양측파대 중 한쪽의 단측파대를 통해 BPSK 변조된 하나의 정보신호를 다른쪽의 단측파대를 통해 다른 BPSK 변조된 정보신호를 동시에 송신하고 수신기에는 하나의 OFDM시스템의 신호처럼 들어온 신호에서 양측파대 각각에서 정보신호를 구분 복조 한다. 또한 각각의 복조된 BPSK 신호는 이론적인 BPSK신호와 거의 유사한 BER 성능을 보인다. 즉 제안하는 시스템 모델은 하나의 BPSK신호를 절반의 스펙트럼만을 사용하여 송신하거나 혹은 두 BPSK신호를 동시에 송신 할 수 있다.