• 한국소음진동공학회논문집
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• 제22권3호
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• pp.275-283
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• 2012

This paper presents a design method of a robust tracking controller satisfying multiple constraints using genetic algorithm. A robust $H_{\infty}$ constraint with loop shaping is used to address disturbance attenuation with error limits and a loop gain constraint is considered so as not to enlarge the tracking loop gain and bandwidth unnecessarily. The robust $H_{\infty}$ constraint is expressed by a matrix inequality and the loop gain constraint is considered as an objective function so that genetic algorithm can be applied. Finally, a robust tracking controller can be obtained by integrating genetic algorithm with LMI approach. The proposed tracking controller design method is applied to the track-following system of an optical DVD recording drive and is evaluated through the experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.747-749
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• 1998

A new $H_{\infty}$ robust controller is proposed by using Sliding Mode Control (SMC). The combination of $H_{\infty}$ with SMC is achieved by proposing a novel sliding surface which has a virtual state. This sliding surface has the nominal dynamics of an original system controlled by $H_{\infty}$ controller. Its design is based on the augumented system whose dynamics have one higher order than that of the original system. The reaching phase is removed by setting an initial virtual state which makes the initial sliding function equal to zero.

• Transactions on Control, Automation and Systems Engineering
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• 제2권1호
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• pp.31-39
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• 2000

We present a robust and reliable H$\infty$ state-feedback controller design for linear uncertain systems, which have norm-bounded time-varying uncertainty in the state matrix, and their prespecified sets of actuators are susceptible to failure. These controllers should guarantee robust stability of the systems and H$\infty$ norm bound against parameter uncertainty and/or actuator failures. Based on the linear matrix inequality (LMI) approach, two state-feedback controller design methods are constructed by formulating to a set of LMIs corresponding to all failure cases or a single LMI that covers all failure cases, with an additional costraint. Effectiveness and geometrical property of these controllers are validated via several numerical examples. Furthermore, the proposed LMI frameworks can be applied to multiobjective problems with additional constraints.

• 전자공학회논문지SC
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• 제39권3호
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• pp.183-190
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• 2002

본 논문에서는 구조화된 어파인(affine) 파라미터 불확실성을 가지는 시변 선형시스템과 구조적 불확실성을 가지는 상태궤환 제어기에 대한 견실 비약성 H∞ 제어기 설계방법을 다루었다. 또한 견실 비약성 H∞ 제어기가 존재할 충분조건, 제어기 설계방법 및 비약성을 만족하는 제어기의 꽉찬 집합(compact set)을 제시하였다. 이 때 제시한 조건은 변수치환과 슈어 여수(Schur complement)정리를 통하여 선형행렬부등식 (LMI : Linear Matrix Inequality)의 계수가 꽉찬 집합 내의 파라미터의 함수로 정의되는 파라미터화 선형 행렬부등식(PLMls: parameterized Linear Matrix Inequalities)으로 표현되므로 분리 볼록개념 (separated convexity concepts)에 기초한 완화기법을 이용하여 유한개의 LMI로 변환하였다. 그리고 본론문에서 제시한 견실 비약성 H∞ 제어기가 제어기이득의 변화에도 불구하고 폐루프시스템의 점근적 안정성 (asymptotic stability)과 외란감쇠 성능을 보장함을 보였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.438-443
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• 2003

In this paper, we propose a control algorithm for two-wheel mobile robot that can move the rider to his or her command and autonomously keep its balance. The control algorithm is based on a mixed $H_2/H_{\infty}$ control scheme. In this control problem the main issue is to move the rider while keeping its balance in the presence of disturbances and parameter uncertainties. The disturbance force caused by uneven road surfaces and the uncertainty due to different rider's heights are considered. To this end we first consider a state feedback controller as a basic framework. Secondly, we obtain the state feedback gain $K_2$ minimizing the $H_2$ norm and the state feedback gain $K_{\infty}$ minimizing the $H_{\infty}$ norm over the whole range of parameter uncertainty. Finally, we select mixed $H_2$/$H_{\infty}$ state feedback controller K as the geometric mean of $K_2$ and $K_{\infty}$. Simulation results show that the mixed $H_2/H_{\infty}$ state feedback controller combines the effects of the optimal $H_2$ state feedback controller and robust $H_{\infty}$ controller state feedback controller efficiently in the presence of disturbance and parameter uncertainty.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.498-503
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• 1993

In this paper, a robust and reliable H$_{\infty}$ control problem is considered for linear uncertain systems with time-varying norm-bounded uncertainty in the state matrix, which performs well despite of actuator outages. Using linear static state feedback and the quadratic stabilization with H$_{\infty}$-norm bound, a robust and reliable H$_{\infty}$ controller is obtained that stabilizes the plant and guarantees an H$_{\infty}$-norm bound constraint on disturbance attenuation for all admissible uncertainties and normal state as well as faulty state of actuators. It provides a sufficient condition for robust and reliable stabilization with H$_{\infty}$-norm bound. Reliability is guaranteed provided actuator outages only occur within a prespecified subset of actuators.tors.

• 한국정보통신학회논문지
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• 제4권5호
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• pp.1111-1116
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• 2000

혼합 $H_2/ H_\infty$ 제어 방법은 $H_2성능과 H_\infty$ -강건성을 결합한 제어기 설계를 위한 적극적인 접근법의 하나이다. 이 논문에서는, 먼저 설계하고자 하는 제어시스템의 추종특성을, 불확실성이 포함된 제어대상에 대하여, $H_2$노름으로 표현하고, 다음으로 $H_\infty$노름으로 제어 시스템의 강건 안정성을 얻도록 하였다. 혼합 $H_2/ H_\infty$ 디지털 제어기는 도립진자 시스템을 제어대상으로 하여 설계하였다. 도립진자 시스템에 대하여 설계한 혼합$H_2/ H_\infty$디지털 제어기는, 불안정 시스템을 안정화하면서 동시에 추종 성능을 향상시키고자 하였다.

• 제어로봇시스템학회논문지
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• 제9권11호
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• pp.868-873
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• 2003

$H_{\infty}$ control has been applied to the design of practical control systems widely because of its robustness. It can minimize $H_{\infty}$ norm of the transfer function between the desired output and the disturbances. The SMC(Sliding Mode Control) is more robust and give the better performance than the $H_{\infty}$ control if the matching condition is satisfied. A controller which can have the advantages of $H_{\infty}$ control and the SMC is proposed to add the robustness of the SMC to the $H_{\infty}$ controller. Its design is based on the augmented system of which dynamics have one higher order than that of the original system and has the same dynamic as the desired system in spite of uncertainties. The dynamic of proposed sliding surface is the same dynamic as the system controlled by $H_{\infty}$ controller without the uncertainties which satisfy the matching condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2191-2193
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• 2004

The Sliding Mode Control is more robust and give the better performance than the $H_{\infty}$ control if the matching condition is satisfied. So in this paper, a controller which can have the advantages of $H_{\infty}$ control and the SMC is proposed to add the robustness of the SMC to the $H_{\infty}$ controller. The dynamic of proposed sliding surface is the same dynamic as the system controlled by $H_{\infty}$ controller without the uncertainties which satisfy the matching condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.331-334
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• 1993

It is a standard problem that designs a controller to minimize the $H_{\infty}$-norm of a given plant. By reducing a standard problem to a model-matching problem, we can obtain all the parameters which consist of a controller. After presenting a practical model and applying it to a tracking model, we design an $H_{\infty}$ controller and an LQ controller to concrete that $H_{\infty}$ control theory is far more robust than LQ control theory. And we show the advantage of an $H_{\infty}$ controller by obtaining a desired Bode diagram and comparing it with that of an LQ controller.