• 한국지능시스템학회논문지
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• 제18권2호
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• pp.151-156
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• 2008

본 논문은 뉴트럴 타입 시간 지연을 가지는 네트워크 기반 시스템의 안정도 분석 및 샘플치 퍼지 제어기 설계 방법에 관하여 논의한다. 먼저 대상이 되는 비선형 네트워크 시스템을 T-S (Takagi-Sugeno) 퍼지 모델로 표현한다. 제안하는 샘플치 퍼지 제어기를 모델링하는 퍼지 규칙과 같은 멤버쉽 함수를 가지게 설계한다. Lyapunov-Krasovskii의 안정화 이론을 도입하여 이를 바탕으로 뉴트럴 형태의 시간 지연을 갖는 T-S 퍼지 시스템의 안정도를 판별한다. T-S 퍼지 시스템의 안정도 조건을 제시하고 선형 행렬 부등식의 형태로 표현한다. 제안된 선형 행렬 부등식의 해를 통하여 샘플치 퍼지 제어기의 이득 값을 설계한다. 마지막으로, 본 논문에서 제안한 방법의 적용 가능성과 일반성을 평가하기 위하여 수치적인 예를 적용한다.

• 제어로봇시스템학회논문지
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• 제22권6호
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• pp.453-462
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• 2016

This paper proposes a torque control method for surface mounted permanent magnetic synchronous motor (PMSM) driven by a 2-level voltage source driven inverter, which has fast torque response and small torque ripple. The proposed torque control method follows the finite control set model predictive control (FCS-MPC) strategy. A reference state is derived at each time step for the given time varying torque reference and the cost index is defined so that the tracking error for this reference state should be penalized. The choice of an optimal output voltage vector is made first from the 6 possible active voltage vectors of the 2-level voltage source inverter. Then a modulation factor for the chosen optimal voltage vector is obtained so that the torque ripple can be reduced further. It is shown that the proposed FCS-MPC control method yields fast torque tracking response and small torque ripple through simulation and experiments.

• 한국지능시스템학회논문지
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• 제26권4호
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• pp.308-315
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• 2016

본 논문은 이산시간 장주기모델로 구성된 다개체시스템의 타카기-수게노(Takagi-Sugeno: T-S) 퍼지 군집제어 기법을 제안한다. 이산시간 모델은 오일러(Euler) 방법을 이용하여 유도한다. 이에 대한 T-S 퍼지 모델은 피드백 선형화 기법을 통해 구성하며, 이를 점근적으로 안정화하기 위한 퍼지제어기를 설계한다. 제어기 설계조건은 선형행렬부등식의 형태로 표현된다.

• Journal of Power Electronics
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• 제16권3호
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• pp.1025-1035
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• 2016

Luenberger observer (LO)-based sensorless multi-loop control of a converter requires an iterative trial-and-error design process, considering that many parameters should be determined, and loop gains are indirectly related to the closed-loop characteristics. Robust H∞ control adopts a compact sensorless controller. The algebraic Riccati equation (ARE)-based and linear matrix inequality (LMI)-based H∞ approaches need an exhaustive procedure, particularly for a low-order controller. Therefore, in this study, a novel robust H∞ synthesis approach is proposed to design a low-order sensorless controller for boost converters, which need not solve any ARE or LMI, and to parameterize the controller by an adjustable parameter behaving like a "knob" on the closed-loop characteristics. Simulation results show the straightforward closed-loop characteristics evaluation and better dynamic performance by the proposed H∞ approach, compared with the LO-based sensorless multi-loop control. Practical experiments on a digital processor confirmed the simulation results.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.229-244
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• 2015

H-infinity norm relates to the maximum in the frequency response function and H-infinity control method focuses on the case that the vibration is excited at the fundamental frequency, while 2-norm relates to the output energy of systems with the input of pulses or white noises and 2-norm control method weighs the overall vibration performance of systems. The trade-off between the performance in frequency-domain and that in time-domain may be achieved by integrating two indices in the mixed vibration control method. Based on the linear fractional state space representation in the modal space for a piezoelectric flexible structure with uncertain modal parameters and un-modeled residual high-frequency modes, a mixed dynamic output feedback control design method is proposed to suppress the structural vibration. Using the linear matrix inequality (LMI) technique, the initial populations are generated by the designing of robust control laws with different H-infinity performance indices before the robust 2-norm performance index of the closed-loop system is included in the fitness function of optimization. A flexible beam structure with a piezoelectric sensor and a piezoelectric actuator are used as the subject for numerical studies. Compared with the velocity feedback control method, the numerical simulation results show the effectiveness of the proposed method.

• Structural Engineering and Mechanics
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• 제29권5호
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• pp.489-504
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• 2008

In piezoelectric flexible structures, the contribution of vibration modes to the dynamic response of system may change with the location of piezoelectric actuator patches, which means that the ability of actuators to control vibration modes should be taken into account in the development of modal reduction model. The spatial $H_2$ norm of modes, which serves as a measure of the intensity of modes to system dynamical response, is used to pick up the modes included in the reduction model. Based on the reduction model, the paper develops the state-space representation for uncertain flexible tructures with piezoelectric material as non-collocated actuators/sensors in the modal space, taking into account uncertainties due to modal parameters variation and unmodeled residual modes. In order to suppress the vibration of the structure, a dynamic output feedback control law is designed by imultaneously considering the conflicting performance specifications, such as robust stability, transient response requirement, disturbance rejection, actuator saturation constraints. Based on linear matrix inequality, the vibration control design is converted into a linear convex optimization problem. The simulation results show how the influence of vibration modes on the dynamical response of structure varies with the location of piezoelectric actuators, why the uncertainties should be considered in the reductiom model to avoid exciting high-frequency modes in the non-collcated vibration control, and the possiblity that the conflicting performance specifications are dealt with simultaneously.

• 제어로봇시스템학회논문지
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• 제6권1호
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• pp.25-34
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• 2000

In this paper, we design a H^\infty servo controller for gauge control of tandem cold mill. To improve the performance of the AGC(Aotomatic Gauge Control) system based on the Taylor linearized model of tandem cold mill, the H^\infty servo controller is designed to satisfy robust stability, disturbance attenuation and robust tracking properties. The H^\infty servo controller problem is modified as an usual H^\infty control problem, and the solvability condition of the H^\infty servo problem depends on the solvability of the modified H^\infty control problem. Since this modified problem does not satisfied standard assumptions for the H^\infty control problem, it is solved by an LMI(Linear Matrix Inequality) technique. Consequently, the comparison between the H^\infty servo controller and the existing PID/FF(FeedForward) controller shows the usefulness of this study.

• Structural Engineering and Mechanics
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• 제56권3호
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• pp.385-407
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• 2015

This paper deals with the problem of the global stabilization for a class of tension leg platform (TLP) nonlinear control systems. It is well known that, in general, the global asymptotic stability of the TLP subsystems does not imply the global asymptotic stability of the composite closed-loop system. Finding system parameters for stabilizing the control system is also an issue need to be concerned. In this paper, we give additional sufficient conditions for the global stabilization of a TLP nonlinear system. In particular, we consider a class of NN based Takagi-Sugeno (TS) fuzzy TLP systems. Using the so-called parallel distributed compensation (PDC) controller, we prove that this class of systems can be globally asymptotically stable. The proper design of system parameters are found by a swarm intelligence algorithm called Evolved Bat Algorithm (EBA). An illustrative example is given to show the applicability of the main result.

• 한국지능시스템학회논문지
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• 제25권6호
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• pp.615-620
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• 2015

본 논문에서는 화력발전소 보일러-터빈 제어시스템의 고장검출 시스템을 설계한다. 이를 위하여 보일러-터빈의 비선형 동특성을 측정 가능한 시변 파라메터를 갖는 T-S 퍼지시스템으로 나타내고 관측기 기반의 고장검출 필터를 사용하여 오차발생기를 설계한다. 고장발생 측정기를 식별하기 위하여 고장검출 필터 출구에 근사적인 역시스템을 연결하였다. 제시한 방법의 효용성을 컴퓨터 모의실험을 통하여 입증한다.

• 한국정보통신학회논문지
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• 제11권2호
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• pp.316-321
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• 2007

[ $H{\infty}$ ] 제어기는 외란이나 잡음에 대해서 강인한 성능을 가지고 있지 만 파라미터 불확실성이 존재하면 제어입력을 구하기가 쉽지 않으며 불확실성의 영향에 따라서 제어 성능에 큰 차이를 보인다. 하지 만 슬라이딩 모드제어는 파라미터 불확실성에 대하여 우수한 강인성을 가지고 있는 제어 기법이다. 그러므로 본 논문에서는 슬라이딩 모드 제어기법을 도입하여 LMI를 이용한 $H{\infty}$ 제어기의 강인성을 향상시킬 수 있는 제어 기법을 제안한다.