• The Journal of the Acoustical Society of Korea
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• v.17 no.1E
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• pp.3-9
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• 1998

In this paper, a robust active noise controller is designed to reduce noise in al small cavity. Noise characteristics in the small cavity are nonlinear and we could get its model with considerable modelling errors. The objective of this paper is to minimize the effects of these modelling errors and maximize the noise reduction performance. The solution could be obtained by the H∞ robust control theory. The resulting feedback controller minimizes the H∞ norm of the mixed sensitivity function, which means the effects of uncertainties of the model are suppressed in the sense of stability and the performance is enhanced as a given specification. The designed controller is realized with analog devices such as Op. Amps and experimental results show that the controller reduces noise signal sufficiently.

• Journal of KSNVE
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• v.4 no.2
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• pp.187-198
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• 1994

This study is to describe the effects of the duct termination conditions conditions upon the active noise attenuation system. The adaptive filtering algorithm using FIR filter is implemented for duct noise attenuation. To avoid the instability caused by the acoustic feedback, two methods are considered. One is to use a compensating FIR filter. The other is to utilize uni-directional detecting microphone and uni-directional control speaker. Experimental results show that the reflections of sound from duct terminations greatly reduce the performance of ANC system. The directionality of detecting microphone and control speaker is a major factor to decide ANC performance. When there are some reflections from both duct terminations, the noise attenuation using finite FIR filter is not enough to model the duct plant. Especially, the reflection from the upstream termination reduces the noise attenuation in the frequencies related to the distance between control speaker and upstream termination. The performance of the noise attenuation is found to be largely enhanced by using uni-directional coupler, both on detecting microphone and control speaker, even if the duct system has an arbitrary termination conditions.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.3118-3120
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• 2000

In this paper. a stable IIR adaptive filter for active noise control is proposed. The IIR filter structure is more effective when acoustic feedback exists, in which case an order of a FIR filter must be very large if some of the poles of the ideal control filter are near the unit circle. But the IIR filter may have stability problems especially when the adaptive algorithm is not converged. A stabilizing procedure for IIR adaptive filter is presented in this paper, and computer simulation is performed to show the effectiveness of proposed schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.9 no.1
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• pp.25-29
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• 1984

The active compensation of operational amplifeir is that it compensates the phase shift and the attennation of gain of OP Amp, according as the frequency increases. The compensation circuit is applied to VCVS and interting integrator. For VCVS, the phase shift of proposed compensated circuit is not concern with the frequency and the gain chracteristic is better than the proposde circuit by Soliman, according as the rate of feedback resistors of compensated circuit changes. Voltage follower accomplishies compgnsation using the same circuit. Also, the compensation circuit to increase O-ffactor in inverting integrator is proposed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.809-823
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• 1991

본 연구에서는 Wiener 필터링 이론에 의하여 소음원의 입력신호에 대한 최적 한 예측을 할 수 있는 최적예측기(optimal predictor)로써 부가적인 음을 발생시키고 입력신호 및 출력신호 간의 차인 오차를 최소화시키도록 하는 적응신호처리방법에 대 해 설명하고 이러한 적응 신호처리 방법을 이용한 능동 소음 제어 방법을 제시하였다. 이와 아울러 제어계의 환경 변화에 따른 파라메타의 변화에 적응적으로 응답이 가능해 야 하는 적응 소음 제어계에서, 음향궤환과 함께 필히 고려해야하는 부가적인 전달함 수-모델과 스피커를 포함하는 보조경로 및 오차미이크로폰을 포함하는 오차경로의 전 달함수의 영향을 고려한 능동소음제어에 대해 연구하였다.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.490-495
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• 1998

In this paper an asymmetric hydraulic actuator which consists of single acting cylinder and servo valve is modeled for a quarter car active suspension system. This model regards the force as an internal state rather than a control input. The control input of the model is the sum of oil flows that pass through the valve's orifices. The resulting dynamic equation in the state space ap-pears a feedback connection of a nominal linear time in-variant term with a nonlinear bounded uncertain block. Since this model makes it possible to eliminate the force control phase, analysis and controller design are made straightforward and simple. Well known LQR method is then applied. Simulation and test rig experiment show the effectiveness of this approach in modeling and control.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.92-99
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• 2001

This paper presents a simulation study using a robust controller to improve the roll stability of a vehicle. The controller is designed in the framework of an output feedback H$_{\infty}$ control scheme based on the 3DOF linear vehicle model, solving the mixed-sensitivity problem to guarantee the robust stability and disturbance rejection with respect to parameter variations due to laden and running vehicle conditions. In order to investigate the feasibility of the active roll control system in a real car, its performance is evaluated by simulation in a 10DOF full vehicle model with actuator dynamics and tire characteristics.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.285-291
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• 2008

Active Queue Management(AQM) has been widely used for congestion avoidance in Transmission Control Protocol(TCP) networks. Although numerous AQM schemes have been proposed to regulate a queue size close to a reference level, most of them are incapable of adequately adapting to TCP network dynamics due to TCP's non-linearity and time-varying stochastic properties. To alleviate these problems, we introduce an AQM technique based on a dynamic neural network using the Back-Propagation(BP) algorithm. The dynamic neural network is designed to perform as a robust adaptive feedback controller for TCP dynamics after an adequate training period. We evaluate the performances of the proposed neural network AQM approach using simulation experiments. The proposed approach yields superior performance with faster transient time, larger throughput, and higher link utilization compared to two existing schemes: Random Early Detection(RED) and Proportional-Integral(PI)-based AQM. The neural AQM outperformed PI control and RED, especially in transient state and TCP dynamics variation.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.435-436
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• 2017

This papaer is study on thermal analysis of the active-front-end(AFE) rectifier for solid-state-transformer(SST) applications. finite element analysis simulation model is combined by switching component model, power diode and heat-sink model. thermal model is calculated by computer program and feedback the result. using simulation result analysis switching loss and compare to thermal diffusion of the heat in the model for steady-state operation.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1018-1020
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• 1996

In this paper, when a robust active noise controller for a small cavity to control the noise induced in the cavity is designed, the Graphical method based on the robust stability and performance requirements is studied. The problem of designing controller that achieve these robust performance conditions is related to minimizing the $H_{\infty}$ norm of the mixed sensitivity function by using $H_{\infty}$ control theory. Also, For design the controller, the loopshaping method which control the weight functions to satisfy the design specification without loss of a robust performance can be used. Therefore, we determined the acceptable design specification with the system characteristics of the small cavity and obtained its robust controller with the robust performance specifications by stability margin.