• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 B
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• pp.475-478
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• 1999

In this paper, we propose the robust performance design of multivariable systems within the framework of Quantitative Feedback Theory(QFT) using ICD. The ICD(Individual Channel Design) is a multivariable control method based on the classical frequence response. It is considered to apply feedforward controller for compensating the effect of interconnection between channels. Performance of the proposed method are demonstrated by simulations in appling gas turbine model.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.440-445
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• 2000

Robust tracking controller of optical disk drive(ODD) is designed using quantitative feedback theory(QFT). Nominal plant model is identified from real system through modal test. Uncertainties and control performance of tracking servo are specified, and robust controller satisfying these specifications is designed in the QFT framework. To verify the performances of designed controller, experiment are performed in a digital signal processor(DSP) environment, and experimental results are compared with simulations.

• 한국초전도ㆍ저온공학회논문지
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• 제15권1호
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• pp.19-24
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• 2013

In this paper, the Superconductor flywheel energy storage system (SFESS) was used for the load frequency control (LFC) of an interconnected 2 area power system. The robust SFESS controller using quantitative feedback theory (QFT) was designed to improve control performance in spite of parameter uncertainty and unexpected disturbances. An overlapping decomposition method was applied to simplify SFESS controller design for the interconnected 2 area power system. The model for simulation of the interconnected 2 area power system included the reheat steam turbine, governor, boiler dynamics and nonlinearity such as governor deadband and generation rate constraint (GRC). To verify robust performance of proposed SFESS controller, dynamic simulation was performed under various disturbances and parameters variation of power system. The results showed that the proposed SFESS controller was more robust than the conventional method.

• Journal of Advanced Marine Engineering and Technology
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• 제25권4호
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• pp.833-845
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• 2001

Quantitative Feedback Theory(QFT) has been used to design a robust power system stabilizer(PSS) to improve transient and dynamic stabilities of a power system. This design technique is basically accomplished in frequency domain. The most important feature of QFT is that it is able to deal with the design problem of complicated uncertain plants. A basic idea in QFT design is the translation of closed-loop frequency-domain specifications into Nichols chart domains specifying the allowable range of the nominal open-loop response and then to design a controller by using the gain-phase loop shaping technique. This paper introduces a new algorithm to compute QFT bounds more efficiently. The propose QFT design method ensures a satisfactory performance of the PSS under a wide range of power system operating conditions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.433-437
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• 2003

Quantitative Feedback Theory (QFT) is one of effective methods of robust controller design. In QFT design we can considers the phase information of the perturbed plant so it is less conservative than $H_{\infty}$ and ${\mu}$-synthesis methods and as be shown, it is more transparent than the sensitivity reduction methods mentioned . In this paper we want to overcome the major drawback of QFT method which is lack of an automatic method for loop-shaping step of the method so we focus on the following problem: Given a nominal plant and QFT bounds, synthesize a controller that achieves closed-loop stability and satisfies the QFT boundaries. The usual approach to this problem involves loop-shaping in the frequency domain by manipulating the poles and zeros of the nominal loop transfer function. This process now aided by recently developed computer aided design tools proceeds by trial and error and its success often depends heavily on the experience of the loop-shaper. Thus for the novice and First time QFT user, there is a genuine need for an automatic loop-shaping tool to generate a first-cut solution. Clearly such an automatic process must involve some sort of optimization, and while recent results on convex optimization have found fruitful applications in other areas of control theory we have tried to use LMI theory for automating the loop-shaping step of QFT design.

• 대한기계학회논문집A
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• 제32권3호
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• pp.280-289
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• 2008

This paper presents design of the quantitative feedback control system of the three axes hydraulic road simulator with respect to the dummy wheel for uncertain multiple input-output(MIMO) feedback systems. This simulator has the uncertain parameters such as fluid compressibility, fluid leakage, electrical servo components and nonlinear mechanical connections. This works have reproduced the random input signal to implement the real road vibration's data in the lab. The replaced $m^2$ MISO equivalent control systems satisfied the design specifications of the original $m^*m$ MIMO control system and developed the mathematical method using quantitative feedback theory based on schauder's fixed point theorem. This control system illustrates a tracking performance of the closed-loop controller with low order transfer function G(s) and pre-filter F(s) having the minimum bandwidth for parameters of uncertain plant. The efficacy of the designed controller is verified through the dynamic simulation with combined hydraulic model and Adams simulator model. The Matlab simulation results to connect with Adams simulator model show that the proposed control technique works well under uncertain hydraulic plant system. The designed control system has satisfied robust performance with stability bounds, tracking bounds and disturbance. The Hydraulic road simulator consists of the specimen, hydraulic pump, servo valve, hydraulic actuator and its control equipments

• 한국자동차공학회논문집
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• 제21권3호
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• pp.88-97
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• 2013

This paper presents a robust air-to-fuel ratio (AFR) control algorithm for managing exhaust gas recirculation (EGR) systems. In order to handle production tolerance, deterioration and parameter-varying characteristics of the EGR system, quantitative feedback theory (QFT) is applied for designing the robust AFR control algorithm. A plant model of EGR system is approximated by the first order transfer function plus time-delay (FOPTD) model. EGR valve position and AFR of exhaust gas are used as input/output variables of the plant model. Through engine experiments, parameter uncertainty of the plant model is identified in a fixed engine operating point. Requirement specifications of robust stability and reference tracking performance are defined and these are fulfilled by the following steps: during loop shaping process, a PID controller is designed by using a nominal loop transmission function represented on Nichols chart. Then, the frequency response of closed-loop transfer function is used for designing a prefilter. It is validated that the proposed QFT-based AFR control algorithm successfully satisfy the requirements through experiments of various engine operating points.

• 조명전기설비학회논문지
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• 제16권4호
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• pp.1-7
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• 2002

정량적 궤환이론(Quantitative Feedback Theory : QFT)은 플랜트 불확실성과 외란에도 불구하고 요구된 시스템의 제어성능을 성취하기 위해서 궤환의 사용을 강조하는 매우 실제적인 설계기법이다. 이 QFT의 루프형성과정은 요구된 경계조건이 만족될 때까지 강인한 제어기를 설계하는 것을 허용한다. 본 논문에서는 QFT의 루프형성을 이용한 PID 제어기의 최적 설계방법을 제안한다. 제안된 방법은 QFT 경계조건에 의해 얻어진 2차원의 시스템 행렬과 출력 벡터를 재배열하는 것으로부터 전개된 선형 연립방정식으로부터 PID 제어기의 파라미터 벡터를 식별하는 방식이다. 제안된 방법의 유용성은 터빈의 속도제어 문제에 의해 검증하였다.

• 전기학회논문지P
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• 제51권2호
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• pp.94-98
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• 2002

QFT(Quantitative Feedback Theory) is a very practical design technique that emphasizes the use of feedback for achieving the desired system performance tolerances in despite of plant uncertainty and disturbance. The gain-phase loop shaping procedure of QFT is employed to design controller, until the bounds at desired frequencies are satisfied. This paper presents a transfer function synthesis using TLS(Total Least Squares) and offers a loop shaping method with the suggested technique. An example illustrates a feasibility of the presented algorithm.

• 한국항공우주학회지
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• 제42권3호
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• pp.243-253
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• 2014

본 논문은 플랜트 파라미터의 불확실성에도 불구하고 강인성을 보장하는 정량적 궤환 이론에 대해 다루고 있다. 정량적 궤환 이론은 플랜트의 파라미터와 외란의 불확실성에 대해 주파수 영역에서 설계 사양의 강인성을 보장한다. 정량적 궤환 이론을 이용하기 위해 선정한 플랜트는 기동성이 뛰어나며 헬리콥터와 같이 수직 이착륙이 가능한 4-회전익 비행체를 이용하였으며, 4개의 블레이드를 구동하는 모터의 파라미터 불확실성을 설정하여 요구사양에 맞는 자세 제어가 가능함을 실험하였다. 또한, 자세 제어에는 4-회전익 비행체의 파라미터 변동 범위와 동작 범위를 고려한 전필터를 사용하였다. 이를 위해 MATLAB에서 정량적 궤환 이론에 의해 제어기를 설계할 수 있는 QFT control toolbox인 QFTCT를 사용하여 각 설계 단계에 대해 소개하고 있다.