• 전자공학회논문지SC
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• 제41권5호
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• pp.19-27
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• 2004

시간지연을 갖는 퍼지 시스템에 대한 지연 종속 퍼지 H₂/H/sub ∞/ 제어기 설계 방법을 제안한다. 지연 종속 Lyapunov 함수를 이용하여 폐루프 시스템의 점근적 안정화뿐만 아니라 H₂ 성능과 H/sub ∞/ 성능을 동시에 만족하는 혼합 H₂/H/sub ∞/ 성능 문제를 고려한다. 제어기의 존재성에 대한 충분조건을 유도하고 선형행렬부등식(LMI: linear matrix inequality)으로 나타낸다. 제어기 설계는 병렬 분산 보상의 개념을 이용하고, 퍼지 제어기는 LMI 해를 구함으로써 바로 구할 수 있다. 지연 종속 퍼지 제어기는 존재 조건을 나타내는 선형 행렬 부등식에 시간지연항의 크기를 포함하고 있으므로 시간지연항의 크기를 고려할 수 있다. 따라서 시간지연의 크기에 상관없이 시스템을 안정화 시키는 지연 독립적인 제어기 보다 더 효과적인 설계방법이다. 제안한 방법의 설계과정 및 타당성을 시뮬레이션 예제를 통하여 나타내고 기존의 시간 지연 독립적인 퍼지 H₂/H/sub ∞/ 제어기 설계 방법 보다 효과적인 방법임을 확인한다.

• 한국지능시스템학회논문지
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• 제25권4호
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• pp.349-354
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• 2015

본 논문은 비선형 시스템을 위한 T-S 퍼지 샘플치 필터의 안정도 조건을 제시한다. 퍼지 시스템과 퍼지 필터 사이의 에러 시스템을 제시하며, 리아푸노프 안정도 해석 기법을 이용해 에러 시스템의 안정도 조건을 선형행렬부등식의 형태로 표현한다. 제안된 안정도 조건은 기존과는 다른 접근법을 이용하며, 더 나은 성능을 보인다. 모의실험을 통해 제안한 기법의 효용성을 검증한다.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.299-308
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• 2007

This study proposes a two-layer hierarchical control system that integrates active front wheel steering and four wheel braking torque control to improve vehicle handling performance and stability. The first layer is a robust model matching controller (R-MMC) based on linear matrix inequalities (LMIs), which optimizes an active front steering angle compensation and a desired yaw moment control, and calculates reference wheel slip for the target wheel according to the desired yaw moment. The second layer is a moving sliding mode controller (MSMC) that can track the reference wheel slip in a predetermined time by commanding proper braking torque on the target wheel to achieve the desired yaw moment. Since vehicle sideslip angle measurement is difficult to achieve in practice, a sliding mode observer (SMO) that requires only vehicle yaw rate as the measured input is also developed in this study. The performance and robustness of the SMO and the integrated control system are demonstrated through comprehensive computer simulations. Simulation results reveal the satisfactory tracking ability of the SMO, and the superior improved vehicle handling performance, stability and robustness of the integrated control vehicle.

• 제어로봇시스템학회논문지
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• 제13권5호
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• pp.487-492
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• 2007

This paper presents the development of digital robust fuzzy controller for uncertain nonlinear systems. The proposed approach is based on the intelligent digital redesign(IDR) method with considering the relaxed stability condition of fuzzy control system. The term IDR in the concerned system is to convert an existing analog robust control into an equivalent digital counterpart in the sense of the state-matching. We shows that the IDR problem can be reduced to find the digital fuzzy gains minimizing the norm distance between the closed-loop states of the analog and digital robust control systems. Its constructive conditions are expressed as the linear matrix inequalities(LMIs) and thereby easily tractable by the convex optimization techniques. Based on the nonquadratic Lyapunov function, the robust stabilization conditions are given for the sampled-data fuzzy system, and hence less conservative. A numerical example, chaotic Lorentz system, is demonstrated to visualize the feasibility of the proposed methodology.

• 제어로봇시스템학회논문지
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• 제19권4호
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• pp.285-289
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• 2013

In switching from the track-seeking or track-jumping control mode to track-following control mode in hard disk drives or optical disk drives, initial values of the feedback controller are tuned to improve the transient response. In general, all the initial values of the controller have been compensated for this purpose. In this paper, by partially compensating initial values of digital controllers, we achieve a good performance of the transient response. In the proposed method for IVC (Intial Value Compensation), LMIs (Linear Matrix Inequalities) are used, which includes conditions for improving the performance of the transient response such as reducing a tracking error and control efforts. We obtain optimal initial values of the controller by solving an optimization problem with constraints represented by only one LMI. Although initial values of the controller are partially compensated, we can show that not only a sufficient performance of the transient response is obtained but also control efforts are diminished. The feasibility of the method is verified by simulation studies.

• 한국지능시스템학회논문지
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• 제11권7호
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• pp.621-627
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• 2001

In this paper, a novel and efficient global intelligent digital redesign technique for a Takagi-Sugeno (TS) fuzzy system is addressed. The proposed method should be notably discriminated from the previous works in that in allows us to globally match the states of the closed-loop TS fuzzy system with the pre-designed continuous-time fuzzy-model-based controller and those with the digitally redesigned fuzzy-model-based controller, and further to guarantee the stabilizability by the redesigned controller in the sense of Lyapunov. Sufficient conditions for the global state-matching and the stability of the digitally controller system are formulated in terns of linear matrix inequalities (LMIs). The Duffing-like chaotic oscillator is simulated and demonstrated, to validate the effectiveness of the proposed digital redesign technique, which implies the safe applicability to the digital control system.

• 한국지능시스템학회논문지
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• 제14권3호
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• pp.298-303
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• 2004

본 논문은 임의의 입력지연을 갖는 Takagi-Sugeno (T-S) 퍼지 시스템의 관측기 기반 출력궤환 제어 시스템을 논의한다. 설계된 연속시간 T-S 퍼지 관측기 시스템을 영차의 샘플/홀드 함수를 이용하여 이산시간 관측기를 설계한다. 이때 플랜트와 관측기의 출력에러가 제어기를 통하여 궤환되기 때문에 이산화 과정에서 발생한 에러를 보정할 수 있다. 여기에서 시스템의 제어 입력은 임의로 변화하는 유한개의 상태를 갖는 마코프 확률과정으로 표현한다. 생성된 시스템의 확률적 안정 가능성 조건은 선형 행렬 부등식의 형태로 표현한다. 이러한 결과를 2자유도 헬리콥터의 모델에 대한 모의실험을 통하여 효용성을 확인한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.588-591
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• 2003

This paper presents a new short-term load forecasting system using data mining. Since the electric load has very different pattern according to the day, it definitely gives rise to the forecasting error if only one forecasting model is used. Thus, to resolve this problem, the fuzzy model-based classifier and predictor are proposed for the forecasting of the hourly electric load. The proposed classifier is the multi-input and multi-output fuzzy system of which the consequent part is composed of the Bayesian classifier. The proposed classifier attempts to categorize the input electric load into Monday, Tuesday$\sim$Friday, Saturday, and Sunday electric load, Then, we construct the Takagi-Sugeno (T-S) fuzzy model-based predictor for each class. The parameter identification problem is converted into the generalized eigenvalue problem (GEVP) by formulating the linear matrix inequalities (LMIs). Finally, to show the feasibility of the proposed method, this paper provides the short-term load forecasting example.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1060-1065
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• 2005

An Independent Administrative Corporation Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is developing light-and-small Autonomous Underwater Vehicles (AUV)$^{1)}$, named 'MR-X1' (Marine Robot Experimental 1), which can cruise, investigate and observe by itself without human's help. In this paper, we consider the motion control problem of 'MR-X1' and derive a controller. Since the dynamic property of 'MR-X1' is changed by the influence of the speed, the mathematical model of 'MR-X1' becomes the nonlinear model. In order to design a controller for 'MR-X1', we generally apply nonlinear control theories or linear control theories with some constant speed situation. If we design a controller by applying Linear Quadratic (LQ) optimal control theory, the obtained controller only compensates t e optimality at the designed speed situation, and does not compensate the stability at another speed situations. This paper proposes a controller design method using Linear Matrix Inequalities (LMIs)$^{2),3),4)}$, which can adapt the speed variation of 'MR-X1'. And examples of numerical analysis using our designed controller are shown.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.672-677
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• 2004

In this paper, a new dual-rate digital control technique for the Takagi-Sugeno (T-S) fuzzy system is suggested. The proposed method takes account of the stabilizablity of the discrete-time T-S fuzzy system at the fast-rate sampling points. Our main idea is to utilize the lifted control input. The proposed approach is to obtain the dual-rate discrete-time T-S fuzzy system by discretizing the overall dynamics of the T-S fuzzy system with the lifted control, and then to derive the sufficient conditions for the stabilization in the sense of the Lyapunov asymptotic stability for this system. An example is provided for showing the feasibility of the proposed discretization method.