• Title, Summary, Keyword: QFT

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Design of Robust QFT Controller to Damp Low Frequency Oscillations of Power System (전력계통의 저주파 진동 억제를 위한 강인하 QFT 제어기 설계)

  • 정형환;이정필;김상효;정문규;안병철
    • Journal of the Korean Society of Marine Engineering
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    • v.25 no.4
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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.

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AN LMI APPROACH TO AUTOMATIC LOOP-SHAPING OF QFT CONTROLLERS

  • Bokharaie, Vaheed S.;Khaki-Sedigh, Ali
    • 제어로봇시스템학회:학술대회논문집
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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.

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A Design of PID Controller using Quantitative Feedback Theory and Turbine Speed Control (정량적 궤환이론을 이용한 PID 제어기 설계 및 터빈 속도제어)

  • 김주식
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.16 no.4
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    • pp.1-7
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    • 2002
  • QFT is a very practical design technique that emphasizes the use of feedback for achieving the desired system performances in despite of plant uncertainties and disturbances. The loop shaping procedure of QFT is employed to design the robust controller, until the desired bounds are satisfied. This paper presents an optimization algorithm for designing PID controller using the loop shaping of QFT. The proposed method identifies the parameter vector of PID controller from a linear system that develops from rearranging the two dimensional system matrices and output vectors obtained from the QFT bounds. The feasibilities of the suggested algorithm are illustrated with a turbine speed control problem.

A Design of PID Controller Using Loop Shaping Method of QFT (QFT의 루프형성법을 이용한 PID 제어기 설계)

  • Kim Ju-Sik;Lee Sang-Hyuk
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.52 no.7
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    • pp.379-384
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    • 2003
  • 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 uncertainties and disturbances. The loop shaping procedure of the QFT method is employed to design the robust controller, until the desired bounds are satisfied. This paper presents a method to estimate the Pm parameters using the loop shaping of the QFT. The proposed method identifies the parameter vector of PID controller from a linear system that develops from rearranging the two dimensional input matrices and output vectors obtained from the QFT bounds. The feasibilities of the suggested algorithm are illustrated with an example.

A Frequency Transfer Function Synthesis of QFT Using Total Least Squares Method (완전최소자승법을 이용한 QFT의 주파수 전달함수 합성법)

  • Kim, Ju-Sik;Lee, Sang-Hyuk
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.8
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    • pp.649-654
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    • 2002
  • The essential philosophy of the QFT(Quantitative Feedback Theory) is that a suitable controller can be found by loop shaping a nominal loop transfer function such that the frequency response of this function does not violate the QFT bounds. The loop shaping synthesis involves the identification of a structure and its specialization by means of the parameter optimization. This paper presents an optimization algorithm to estimate the controller parameters from the frequency transfer function synthesis using the TLS(Total Least Squares) in the QFT loop shaping procedure. The proposed method identifies the parameter vector of the robust controller from an overdetermined linear system developed from rearranging the two dimensional system matrices and output vectors obtained from the QFT bounds. The feasibility of the suggested algorithm is illustrated with an example.

Robust QFT(Quantitative Feedback Theory) Controller Design of Parallel Link (평행링크 매니퓰레이터의 강인한 QFT(Quantitative Feedback Theory)제어기 설계)

  • Kang, Min-Goo;Byun, Gi-Sik
    • Proceedings of the KIEE Conference
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    • pp.2249-2251
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    • 2001
  • This paper proposes that it minimizes interference between link at high speed trajectory tracking of 2-degree parallel link manipulator and QFT(Quantitative Feedback Theory) controller which robust structure uncertainty and disturbance of plant. And using ICD(Individual Channel Design), it separates two channel from multivariable system, parallel link manipulator and designs robust controller with applying MISO QFT to each channel. Finally, we make sure of robustness and excellence of QFT controller through simulation and experiment.

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QFT-based Robust Flight Control in C.G Variation of an Aircraft (QFT를 이용한 비행체 무게중심변화에 대한 강인한 제어기 설계)

  • Kim, Min-Soo;Hong, Sung-Kyung;Chung, Chan-Soo
    • Proceedings of the KIEE Conference
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    • pp.2164-2166
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    • 2004
  • QFT는 플랜트의 변동을 고려하여 주파수 영역에서 설계하는 제어기법으로 파라미터의 변화 및 외란에 강인한 제어기 설계에 적합한 제어기 설계 방법이다. 본 논문에서는 종축 방향의 항공기 무게 중심이 변화하는 범위에 대하여 요구 비행성(Flying Quality)을 만족하도록 하는 강인한 QFT 제어기의 설계기법을 제안하였다. 시뮬레이션을 통하여 제안한 QFT 제어기가 무게중심의 변화 범위에서 주어진 비행성능을 만족함을 확인하였다.

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Discordance between Tuberculin Skin Test and Interferon-gamma Release Assays for Diagnosis of Tuberculosis Infection in Korean Children (국내 소아 결핵감염 진단에서의 결핵피부반응 검사와 Interferon-gamma Release Assay (IGRA)의 비교 연구)

  • Yoo, Reenar;Kim, Joon-Il;Kim, Seohee;Lee, Jina
    • Pediatric Infection and Vaccine
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    • v.23 no.1
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    • pp.18-24
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    • 2016
  • Purpose: There is a the great diagnostic challenge in pediatric tuberculosis especially in high burden setting. The purpose of this preliminary study is to evaluate the agreement between tuberculin skin test (TST) and interferon-gamma release assay (IGRA) including T-SPOT$^{(R)}$.TB and QuantiFERON$^{(R)}$-TB Gold (QFT-G) in Korean children. Method: This retrospective study included children and adolescents who visited to Asan Medical Center to evaluate tuberculosis infection using at least two assays of TST, T-SPOT.TB and QFT-G, from January 2014 to April 2015. Results: A total of 20 patients were included, whose median age was 13.3 years (range, 3.8-18.1 years), and all of them had history of BCG vaccination. Eleven patients had underlying diseases including 7 patients with immunosuppressant medication. The concordance rate between T-SPOT.TB and QFT-G was 90%. However, the concordance rate between TST and T-SPOT.TB was 50%, and between TST and QFT-G was 42.9%. Specificity for the diagnosis of tuberculosis infection of T-SPOT.TB, QFT-G, and TST was 93.3%, 86.7%, and 58.3%, respectively. Conclusions: Although there was a discrepancy between TST and IGRA to diagnose tuberculosis, agreement between T-SPOT.TB and QFT-G was relatively high. Further prospective study to validate the clinical usefulness of each assay for immunologic evidence of tuberculosis infection in Korean children will be mandatory.

Study for Position Control of Two-degree Parallel Link Robot Using QFT(Quantitative Feedback Theory) (QFT(Quantitative Feedback Theory)를 이용한 2 자유도 평행 링크 로봇의 위치 제어에 관한 연구)

  • 강민구;변기식;최연욱;황용연
    • Proceedings of the Korea Institute of Convergence Signal Processing
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    • pp.97-100
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    • 2001
  • This paper introduces that it minimizes interference between links at high speed trajectory tracking of 2-degree parallel link robot. And in spite of system uncertainty, it introduces controller design method which is satisfied with performance specification. To do these, we separate two channels from parallel link robot through ICD(Individual Channel Design) and design controller of each channel using QFT(Quantitative Feedback Theory). Finally, we make sure of robustness and excellence of QFT control1er through simulation and experiment.

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Performance Evaluation of TDX-families DTMF Receiver with the QFT (QFT를 이용한 TDX-계열 교환기용 DTMF 수신기의 성능평가)

  • 윤달환
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.26 no.11C
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    • pp.133-139
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    • 2001
  • The economical detection of dual-tone multi-frequency(DTMF) signals is an important factor when developing cost-effective telecommunication equipment. Each channel has independently a DTMF receiver, and it informs the detected signal to processors. In order to detect the DTMF signals, this paper analyze the power spectra of the DTMF receiver by using the QFT algorithm. As experimental result, by analyzing 2$\^$M/ real data in terms of ITU-T specification, it show that the QFT algorithm improve the performance of the DTMF receiver and can save memory waste and can the real-time processing.

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