• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.1085-1089
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• 2007

An acoustic topology optimization method is developed to optimize the acoustic attenuation capability of a muffler. The transmission loss of the muffler is calculated by using the three-point method based on finite element analysis. Each element of the finite element model is assumed to have the variable acoustic properties, which are penalized by a carefully-selected interpolation function to yield clear expansion chamber shapes at the end of topology optimization. The objective of the acoustic topology optimization problem formulated in this work is to maximize the transmission loss at a target frequency. The transmission loss value at a deep frequency of a nominal muffler configuration can be dramatically increased by the proposed optimization method. Optimal muffler configurations are also obtained for other frequencies.

• 전기학회논문지P
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• 제58권4호
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• pp.385-390
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• 2009

This paper presents a novel active noise control (ANC) system using least mean square (LMS) algorithm and neural network approach for decreasing acoustic noise signals inside high-speed trains. We construct a LMS framework as a nominal ANC system and additionally design an artificial single-layered perceptron model as an auxiliary ANC which is aimed to reduce real-time residuary noise due to its nonstationary and uncertain nature. Parameter vector of the hybrid ANC is determined through online estimation to realize an adaptive ANC configuration by means of the steepest descent algorithm. We achieve simulation experiment to demonstrate the proposed ANC system employing realistic acoustic noise signals measured in Korea Train eXpress (KTX).

• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.197-208
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• 1998

Ground track manintenance maneuver simulations for the KOMPSAT spacecraft are performed for three and half years. Both longitude targeting and time targeting strate-gies are applied for in-plane maneuvers. The nominal longitude bands of maneuvers for $\pm5km$ and $\pm10km$ are applied for the longitude targeting and the 21-day maneuver time duration is used for the time targeting. Daily solar flux values for the simulation period are derived from the previous solar cycle values. Atmospheric drag formula for the KOMPSAT orbit altitude is derived from Jacchia model using polynomial and sinusoidal curve fitting. Total required delta velocity and proper time between successive maneuvers are estimated during ground track maintenance maneuver simulations.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.64-69
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• 1993

In this paper we present the performance bounds of the optimal FIR filter in continuous time systems with modeling uncertainty. The performance measure bounds are calculated from the estimation error covariance bounds of the optimal FIR filter and the suboptimal FIR filter. Performance error bounds range are expressed by the upper bounds on the estimation error covariance difference between the real and nominal values in case of the systems with noise uncertainty or model uncertainty. The performance bounds of the systems are derived on the assumption that the system uncertainty and the estimation error covariance are imperfectly known a priori. The estimation error bounds of the optimal FIR filter is compared with those of the Kalman filter via a numerical example applied to the estimation of the motion of an aircraft carrier at sea, which shows the former has better performances than the latter.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.445-448
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• 1996

For a lightly damped system, IIR based filter can have better performance than FIR filter as an adaptive filter in ANC algorithm. IIR based filter which has an infinite impulse response can model a lightly damped acoustic system with a small number of weights compared that of FIR filter and has no nonlinearity and instability problems on weight updating process which are associated to the conventional IIR filters. There are, however, some drawbacks such as design parameters to be determined earlier to get better performance and much increased computational power especially in the presence of error path. In this study, base filter parameters are determined in systematic manner, with the knowledge of the nominal impulse response of the system which should be identified, by Prony's method. Three methods reducing the computational load are proposed and their performance and application limits are discussed. Simulation and experimental results demonstrate the feasibility of the proposed method.

• 제어로봇시스템학회논문지
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• 제5권5호
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• pp.511-520
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• 1999

An anti-reset windup (ARW) based compensation method for state constrained control systems is studied. First, a linear controller is constructed to give a desirable nominal performance ignoring state-constraints of a plant. Then, an additional compensator is introduced to provide smooth performance degradation under state-constraints of the plant. This paper focuses on the effective design method of the additional compensator. By minimizing a reasonable performance index, the proposed compensator is expressed in terms of theplant and ocntroller parameters. The resulting dynamics of the compensated controller exhibits the dominant part of the linear closed-loop system which can be seen from the singular perturbation model reducton theory. THe proposed method guarantees total stability of overall resulting systems if linear controllers were constructed to meet certain condition.

• Transactions on Control, Automation and Systems Engineering
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• 제2권3호
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• pp.175-181
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• 2000

This paper investigates the robust nonlinear H$_{\infty}$ filter with FIR(Finite Impulse Response) structure for nonlinear discrete time-varying uncertain systems represented by the state-space model having parameter uncertainty. Firstly, when there is no parameter uncertainty in the system, the discrete-time nominal nonlinear H$_{\infty}$ FIR filter is derived by using the equivalence relationship between the FIR filter and the recursive filter, which corresponds to the standard nonlinear H$_{\infty}$ filter. Secondly, when the system has the parameter uncertainty, the robust nonlinear H$_{\infty}$ FIR filter is proposed for the discrete-time nonlinear uncertain systems.

• 제어로봇시스템학회논문지
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• 제6권11호
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• pp.968-973
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• 2000

Fault diagnosis plays an important role in the performance and safe operation of many modern engineering plants. This paper investigates the problem of fault detection using neural networks in dynamic systems. A general framework for constructing a nonlinear fault detection scheme for nonlinear dynamic systems containing modeling uncertaintly is proposed. The main idea behind the proposed approach is to monitor the physical system with an off -line learning neural network and then to approximate the upper and lower thresholds of acceleration of the nominal system with the model-based threshold(ThMB) method, The performance of the proposed fault detection scheme is investigated through simulations of a pendulum with uncertainty.

• 전자공학회논문지SC
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• 제40권4호
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• pp.243-250
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• 2003

본 논문에서는 RBF 신경망 외란 관측기를 이용한 영구자석형 동기모터의 속도추종 제어기를 제안한다. 먼저 공칭 모델에 대하여 입출력 선형화에 기반한 속도 제어기를 설계하고 RBF 신경망 외란 관측기에 의해 시스템의 블확실성을 보상한다. 시스템의 파라미터와 부하 토크의 변동을 동시에 추정하는 RBF 신경망 외란 관측기를 이용함으로써 제안한 제어 알고리즘은 시스템의 불화실성에 강인한 특성을 갖는다. 마지막으로 모의실험을 통하여 제안된 제어기의 타당성을 검증한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.267-271
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• 2000

A part definition must not only provide shape information of a nominal part but also contain non-shape information such as tolerances, surface roughness and material attributes. Although machining features are useful for suitable shape information for process reasoning in the CAPP, they need to be integrated with tolerance information for effective process planning. We develop the tolerance modeler that efficiently integrates machining features with tolerance information for feature-based CAPP It is based on the association of machining features, tolerance features. and tolerances Tolerance features, where tolerances are assigned, are classified into two types; one is the face that is a topological entity on a solid model and the other is the functional geometry that is not referenced to topological entities. The functional geometry is represented by using machining features All the data for representing tolerance information with machining features are stored completely and unambiguously in the independent tolerance structure. The developed tolerance modeler is implemented as a module of a comprehensive feature-based CAPP system.