• 융합신호처리학회논문지
• /
• 제2권3호
• /
• pp.57-64
• /
• 2001

본 논문은 시스템의 불확실성과 외란의 불확실성에도 불구하고 원하는 시스템 성능을 만족할 수 있는 강인한 제어기 설계에 대하여 서술한다. QFT(Quantitative Feedback Theory)에 근거한 강인한 제어기 설계과정은 시스템 파라미터 변동과 설계사양을 고려하여 결정되는 템플레이트, 한계조건 그리고 루프형성을 거친다. 설계된 제어기의 성능을 입증하기 위해 파라미터 변동에 매우 민감하고, 비선형성이 강하며 불안정한 특성을 지닌 도립진자시스템에 대하여 적용한다. 설계된 제어기에 대한 시뮬레이션과 실험결과들은 파라메파 변동과 외란에 강인한 제어성능을 보인다.

• 한국정밀공학회지
• /
• 제21권1호
• /
• pp.109-115
• /
• 2004

Polishing process has been applied to get extremely fine surfaces, e.g., mirror surfaces such as optical mirrors, lens, molds and etc. Nowadays not only fine surface quality but also submicron order of dimensional accuracy is required for many applications. To meet the requirements polishing process should be provided with an active control of polishing pressure especially for automation of polishing process. In this paper a study on development of an active polishing pressure control system has been presented. A new type of tool assembly has been developed to facilitate the control. The tool is attached to an axis of a polishing machine with a coil spring and control of the polishing pressure is done by the position control of the axis, which needs no additional actuator. The polishing pressure is successfully measured by the measurement of the spring deformation. Control specifications were quantitatively considered by weighting functions and a controller was designed by using loop-shaping technique based on the no synthesis. Some experiments have been executed on a polishing machine with a PC-NC controller. It is shown that the results were coincident well with the theoretical analyses and satisfied the design specifications.

• 대한전기학회논문지:전력기술부문A
• /
• 제51권9호
• /
• pp.441-450
• /
• 2002

In this paper, optimal tuning problem of power system stabilizer using IA-QFT is investigated to improve power system dynamic stability in spite of parameter variation and disturbance uncertainties. The most important feature of QFT is that it is able to deal with the design problem of complicated uncertain plants. However, loop shaping is currently performed in computer aided design environments manually and it is usually a trial and error procedure. It is difficult to design a controller to satisfy all specifications manually. To solve this problem, a study of design automation using IA needs to be taken into account. The robustness of the proposed controller has been investigated on a single machine infinite bus model. The results are shown that the proposed PSS using IA-QFT is more robust than conventional PSS.

• 대한기계학회논문집A
• /
• 제21권10호
• /
• pp.1683-1693
• /
• 1997

In this paper, a new nonlinear dynamic model is derived for a 2-dimensional overhead crane based on a new definition of 2-degree-of-freedom swing angle, and a new anti-swing control law is proposed for the crane. The dynamic model and control law take simultaneous travel and traverse motions of the crane into consideration. The model is first linearized for small motions of the crane load about the vertical stable equilibrium. Then the model becomes decoupled and symmetric with respect to the travel and traverse axes of the crane. From this result, a decoupled anti-swing control law is proposed based on the linearized model via the loop shaping and root locus methods. This decoupled method guarantees not only fast damping of load-swing but also zero steady state position error with optimal transient response for the 2-dimensional motion of the crane. Finally, the proposed control method is evaluated by controlling the simultaneous travel and traverse motions of a 2-dimensional prototype overhead crane. The effectiveness of the proposed control method is then proven by the experimental results.

• 대한기계학회논문집A
• /
• 제21권2호
• /
• pp.297-304
• /
• 1997

This paper presents a systematic design method of an anti-swing control law for overhead cranes. A velocity servo system for the trolley of a crane is designed based on the dynamics of the trolley and its load. The velocity servo system compensates for the effects of load swing on the trolley dynamics so that the velocity servo is independent of load swing. The velocity servo system is used for the design of a position servo system for the trolley via the loop shaping method. The position servo system and the swing dynamics of the load are then used to design an angle control system for load swing based on the root locus method. The combined position servo and the angle control systems constitute the overall control system. In the presence of low frequency disturbances, the proposed control law guarantees accurate position control for the trolley and fast damping for load swing. Furthermore, the performance of the proposed control law is independent of the mass of the load. Experimental results on a prototype crane show the effectiveness of the proposed anti-swing control law.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제9권5호
• /
• pp.525-536
• /
• 2017

Course keeping is hard to implement under the condition of the propeller stopping or reversing at slow speed for berthing due to the ship's dynamic motion becoming highly nonlinear. To solve this problem, a practical Maneuvering Modeling Group (MMG) ship mathematic model with propeller reversing transverse forces and low speed correction is first discussed to be applied for the right-handed single-screw ship. Secondly, a novel PID-based nonlinear feedback algorithm driven by bipolar sigmoid function is proposed. The PID parameters are determined by a closed-loop gain shaping algorithm directly, while the closed-loop gain shaping theory was employed for effects analysis of this algorithm. Finally, simulation experiments were carried out on an LPG ship. It is shown that the energy consumption and the smoothness performance of the nonlinear feedback control are reduced by 4.2% and 14.6% with satisfactory control effects; the proposed algorithm has the advantages of robustness, energy saving and safety in berthing practice.

• 조명전기설비학회논문지
• /
• 제12권4호
• /
• pp.106-113
• /
• 1998

원자력발전소의 증기발생기 수위제어계는 과도상태뿐만 아니라 정상운전 시에도 제어계 설계에 사용된 모델링이나, 이론의 적용이 매우 어려운 계통이다. 따라서 기존의 제어방법으로는 안정성에 대한 의문이 제기되어 많은 연구가 이루어지고 있다. 이러한 문제점에 입각하여 본 연구에서는 유전 알고리즘을 이용한 개선된 루프 형성법을 제안하고 이 방법올 QFT에 적용하여 제어성능을 향상시킬 수 있는 제어계를 설계하였다. 그리고 시뮬레이션 결과로부터 안정성과 효과적인 제어성능을 얻었다.

• 한국전자파학회논문지
• /
• 제8권6호
• /
• pp.645-655
• /
• 1997

본 논문에서는 CDMA 시스댐에 적용하기 위해 기저 대역에서 설계된 비동기식 동기 추적 회로의 성능을 이론적으로 분석하고 컴퓨터 시뮬레이션을 통해 검증한다. AWGN 채널 환경에서 지터 분산을 펼스 성형 필터, 타이밍 오프셋, 신호 대 잡음 비, 루우프 필터 계수의 함수로 이론적으로 유도하고 2차 동기 추적 회로를 중심으로 루우프 필터의 설계에 판해 고찰한다. 끝으로, 설계된 동기 추적 회로를 ETRI에서 IMT-2000을 위해 설계한 동기식 CDMA 시스템의 역방향 링크에 적용하여 AWGN과 레일라이 페이딩 환경에서의 성능을 시율레이션을 통해 검증한다.

• International Journal of Control, Automation, and Systems
• /
• 제5권6호
• /
• pp.607-613
• /
• 2007

Eigenstructure assignment provides the advantage of allowing great flexibility in shaping the closed-loop system responses by allowing specification of closed-loop eigenvalues and corresponding eigenvectors. But, the general eigenstructure assignment methodologies cannot guarantee stability robustness to parameter variations of a system. In this paper, we present a novel method that has the capability of exact assignment of an eigenstructure which can consider the probability of instability for LTI (Linear Time-Invariant) systems. The probability of instability of an LTI system is determined by the probability distributions of the closed-loop eigenvalues. The stability region for the system is made probabilistically based upon the Monte Carlo evaluations. The proposed control design method is applied to design a flight control system with probabilistic parameter variations to confirm the usefulness of the method.

• 한국항행학회논문지
• /
• 제1권1호
• /
• pp.70-80
• /
• 1997

본 논문에서는 CDMA 이동전파 환경에서 두 가지 비동기식 동기 추적 회로 즉, TCTL과 MCTL의 성능을 비교, 분석한다. 먼저, 두 가지 방식에 대해 안정 상태에서의 지터 분산을 펄스 성형 필터, 타이밍 오프셋, 신호 대 잡음 비 및 루우프 대역폭의 함수로 이론적으로 유도한다. 또한, 루우프 필터의 설계 방법에 대해 2차 동기 추적회로를 중심으로 고찰한다. 끝으로, 동기 추적 오차에 의한 BER 성능 저하를 ETRI 에 의해 IMT-2000용으로 설계된 CDMA 시스템의 역방향 링크에 대해 분석한다.