• Smart Structures and Systems
• /
• 제1권3호
• /
• pp.235-256
• /
• 2005

The non-linear behaviour of electrorheological (ER) and magnetorheological (MR) dampers makes it difficult to design effective control strategies, and as a consequence a wide range of control systems have been proposed in the literature. These previous studies have not always compared the performance to equivalent passive systems, alternative control designs, or idealised active systems. As a result it is often impossible to compare the performance of different smart damper control strategies. This article provides some insight into the relative performance of two MR damper control strategies: on/off control and feedback linearisation. The performance of both strategies is benchmarked against ideal passive, semi-active and fully active damping. The study relies upon a previously developed model of an MR damper, which in this work is validated experimentally under closed-loop conditions with a broadband mechanical excitation. Two vibration isolation case studies are investigated: a single-degree-of-freedom mass-isolator, and a two-degree-of-freedom system that represents a vehicle suspension system. In both cases, a variety of broadband mechanical excitations are used and the results analysed in the frequency domain. It is shown that although on/off control is more straightforward to implement, its performance is worse than the feedback linearisation strategy, and can be extremely sensitive to the excitation conditions.

• 전기학회논문지P
• /
• 제59권1호
• /
• pp.64-70
• /
• 2010

This paper presents how to decide on tuning factor(${\delta}$) and quality factor(Q) values in design of single-tuned passive harmonic filters. Tuning factor(${\delta}$) and quality factor(Q) values have to consider before decision on circuit parameters of passive filters. A Study on these two value has not been scarcely performed and only experienced values has been used in passive harmonic filter design by far. As a experienced value, in cases of 5th and 7th filter, tuning factor(${\delta}$) is about 0.94 and 0.96 respectively and quality factor(Q) is, in all cases of, 50. If Single-tuned passive harmonic filter will be off-tuned, performance of filter will be decreased steeply and occur to parallel resonance between system reactance and filter capacitance. Therefore During the operation, In order not to off-tuning, Filter must be tuned at former order than actual tuning order. This is the same that total impedance of filter must have a reactive impedance. In this paper, Tuning factor(${\delta}$) is decided via example of real system and using the bode-plot and then performance of filters confirmed by filter current absorbtion rate. And Quality factor(Q) decided using the bode plot in example system and then performance of filters confirmed by filter current absorbtion rate also, which makes a calculated filter parameters to satisfy IEEE-519 distortion limits. Finally, Performance of the designed passive harmonic filter using the tuning factor(${\delta}$) and quality factor(Q) values, decided in this paper is verified by experiment and shows that 5th, 7th, 9th, 11th and 13th current harmonic distortions are decreased within IEEE-519 distortion limits, respectively.

• 대한기계학회논문집B
• /
• 제35권6호
• /
• pp.593-601
• /
• 2011

다양한 작동 조건에서 고분자 전해질형 연료전지의 성능 변화를 예측하기 위한 해석 프로그램을 구성하여 열관리가 시스템의 성능에 미치는 영향을 해석하였다. 전체 시스템은 연료전지 스택, 공기공급계, 연료공급계, 열 관리계로 구성 되었으며 각 구성부의 설계점을 고려하여 열역학적 모델링을 적용 하였다. 외기온 변화와 냉각 시스템의 성능 변화에 따라 연료전지 스택의 온도 및 출력 변화가 예상되므로 탈설계 해석을 하여 전체 시스템의 성능 변화를 예측하였다.

• 한국산업정보학회논문지
• /
• 제24권5호
• /
• pp.95-104
• /
• 2019

본 논문에서는 잔향 환경에 강인한 GSFM(Generalized sinusoidal frequency modulated) 펄스를 설계하는 기법을 제안하였다. GSFM 펄스는 SFM(Sinusoidal frequency modulated) 펄스의 일반화한 형태로써 거리와 도플러 분해능이 모두 우수한 압정형태의 모호성 함수를 가지는 장점이 있다. 하지만 일반화를 하는 과정에서 주기성이 사라지기 때문에, 빗살형태의 스펙트럼을 가지는 SFM 펄스에 비해 잔향환경에서 탐지 성능이 저하된다. 본 논문에서는 GSFM 펄스의 파라미터 ${\rho}$를 적절히 변화시켜 SFM 펄스의 잔향 제거 성능과 GSFM 펄스의 거리 분해능 성능 간에 트레이드오프(Trade-off)관계를 분석하고, 비교적 높은 성능을 동시에 만족할 수 있는 ${\rho}$ 값을 제안하였다. 제안한 GSFM 펄스의 성능을 검증하기 위해 잔향환경을 모의하여 시뮬레이션을 수행하였으며, 제안한 GSFM 펄스가 저속의 도플러 표적을 탐지하면서 우수한 거리 분해능을 가지는 것을 확인할 수 있었다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년 영문 학술대회
• /
• pp.213-217
• /
• 2008

This paper describes an application of centrifugal compressor optimization system, in which the blade profile of impeller is represented with NURBS(Non-Uniform Rational B-Spline) curve. A commercial CFD(Computational Fluid Dynamics) program named NUMECA fine/turbo was used to evaluate the performance of the whole centrifugal compressor flow passage including impeller and diffuser. The whole optimization design system was integrated based on iSIGHT, a commercial integration and optimization software, which provides a direct application of some optimization algorithms. To insure the practicability of optimization, the performance of centrifugal compressor under all condition was concerned during the optimizing process. That means a compositive object function considering the aerodynamic efficiency, pressure ratio and mass flow rate under different work condition was applied by using different weight number for different conditions. Using the optimization method described in this paper, an optimized design of the impeller blade of centrifugal compressor was obtained. Comparing to the original design, optimized design has a better performance not only under the design work condition, but also the off-design work condition including near stall and near choke condition.

• Advances in aircraft and spacecraft science
• /
• 제10권3호
• /
• pp.245-256
• /
• 2023

In order to improve aerodynamic performance of multi-stage axial flow turbines used in aircraft engines, a one-dimensional aerodynamic design and optimization framework is constructed. In the method, flow path is generated by solving mass continuation and energy conservation with loss computed by the Craig & Cox model; Also real gas properties has been taken into consideration. To obtain an optimal result, a multi-objective genetic algorithm is used to optimize the efficiencies and determine values of various design variables; Final design can be selected from obtained Pareto optimal solution sets. A three-stage axial turbine is used to verify the effectiveness of the developed optimization framework, and designs are checked by three-dimensional CFD simulation. Results show that the aerodynamic performance of the optimized turbine has been significantly improved at design point, with the total-to-total efficiency increased by 1.17% and the total-to-static efficiency increased by 1.48%. As for the off-design performance, the optimized one is improved at all working points except those at small mass flow.

• 한국추진공학회지
• /
• 제13권5호
• /
• pp.57-63
• /
• 2009

본 논문에서는 항공기 POD용 환경조절장치의 개발을 위한 모델링 및 시뮬레이션에 관한 연구를 수행하였다. 먼저, 시스템 요구성능을 분석하여 ACM 방식의 환경조절장치를 구성하고 성능모사를 위한 모델링을 수행하였다. 다음으로 각 구성품의 개념설계를 위해 주요구성품의 성능변화에 따른 민감도를 분석하고 시스템 요구성능을 만족하는 설계점 성능을 결정하였다. 다양한 비행환경에서의 탈설계 성능 모사를 통해 전체 운용영역에서의 개념설계 타당성을 검토하고 천이 성능해석을 통해 동적 거동특성을 분석하였다.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
• /
• pp.1166-1169
• /
• 2005

This paper describes a new transient voltage suppressor(TVS) with a low insertion loss and a high cut-off frequency to protect antenna circuit from transient voltages. Conventional protection devices have some problems such as a low frequency bandwidth and a high insertion loss. In order to improve these limitations, a coaxal type TVS, which consists of a gas tube is developed. The performance of the proposed transient voltage suppressor is tested by using a combination surge generator specified in IEC 61000-4-5 standard and by using a network analyzer of 40 MHz ${\sim}$ 5 GHz bandwidth. From the experimental results, it is confirmed that the proposed TVS has an enough protection performance in a low insertion loss and a high cut-off frequency.

• 전자공학회논문지D
• /
• 제35D권12호
• /
• pp.53-58
• /
• 1998

다결정 실리콘 박막 트랜지스터를 이용한 회로의 성능 향상을 위하여 새로운 구조의 4-terminal buried channel poly-Si TFT(BCTFT)를 설계하고 제작하였다. BCTFT는 moderate 도핑이 된 buried channel을 이용하므로 기존의 다결정 실리콘 TFT보다 ON-전류와 전계 효과 이동도가 n-형과 p-형 소자 각각 5배와 10배 향상되었다. BCTFT는 moderate 도핑된 buried 채널과 counter 도핑된 body 사이의 junction 공핍에 의하여 캐리어의 이동이 억제 되므로 OFF-전류가 증가하지 않았다.

• 한국지능시스템학회:학술대회논문집
• /
• 한국퍼지및지능시스템학회 2002년도 추계학술대회 및 정기총회
• /
• pp.179-182
• /
• 2002

In this paper, this system makes use of the analog sensor and converts the feature of fish analog signal when sensor is operating with CPU(80C196KC). Then, After signal processing, this feature Is classified a special feature and a outline of fish by using the neural network, one of the artificial intelligence scheme. This neural network classifies fish pattern of very simple and short calculation. This has linear activation function and the error backpropagation is used as a learning algorithm. And the neural network is learned in off-line process. Because an adaptation period of neural network is too long time when random initial weights are used, off-line learning Is induced to decrease the Progress time We confirmed this method has better performance than somewhat outdated machines.