• Journal of Institute of Control, Robotics and Systems
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• v.5 no.2
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• pp.139-144
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• 1999

The present paper is concerned with the robust decentralized stabilization problem of large-scale systems with time delays in the interconnections using sliding mode control. Based on Lyapunov stability theorem and H$_{\infty}$ theory, an existence condition of the sliding mode and a robust decentralized sliding mode controller are newly derived for large-scale systems under mismatched uncertainties. Finally, a numerical example is given to verify the validity of the results developed in this paper.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.6
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• pp.502-508
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• 2001

In this paper, slack is computed from a comparison of the cable pay out rate and the ship ground speed in accordance with laying conditions, and the speed controller of the cable engine based on an H(sub)$\infty$ servo control id designed for adjusting the cable engine in order to lay a desired amount of slack. The controller is designed for robust tracking of the cable engine under disturbances. The performance of the designed controller is evaluated by computer simulation, and, consequently, a feasibility study for laying the submarine cable stably is done through analyzing simulation results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.255-259
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• 1996

This paper presents active vibration control of a rotating cantilevered beam using piezoceramic actuators. A governing equation of motion is obtained by the Hamilton's principle and expressed in the state space representation. Subsequently, an H$_{\infty}$ control which is robust to system uncertainties is synthesized through the loop shaping design procedure. Computer simulations for the steady-state vibration control are undertaken in order to demonstrate the effectiveness and robustness of the proposed control methodology..y.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.95.3-95
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• 2001

This paper investigates the simultaneous use of mixed H2/H_inf and mu-synthesis design methodology to design a robust controller for flexible link. We adopt four steps to design control system as follows: Step 1 : Generally, there are differences between the nominal and real model, so we consider the plant as a combination of parametric model uncertainty and unstructured uncertainty represents real structural uncertainties associated with the damping ratios of the flexible modes retained in the nominal model without payload. denotes the uncertainty which is due to the payload added at the tip. Step 2 : We adopt the mixed H2/H_inf theory to design a feedback controller K(s) by using the model uncertainty ...

• ICROS
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• v.1 no.2
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• pp.21-29
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• 1995

이 글에서는 H/sub .inf./ 설계법의 장단점에 대해서 알아보았다. H/sub .inf./ 제어기법은 이론적인 연구와 함께 산업응용에 관한 연구도 활발하여, 자동차 제어, 항공우주 제어(고성능 헬리콥터의 비행제어, 비행체의 핏치축 제어, 우주구조물체의 제어), 공정제어(발전소에서의 핵반응로 제어), 및 기계제어 등에 광범위하게 응용되고 있다. H/sub .inf./ 제어기법은 여타의 다른 제어기 설계기법에 비해 많은 수학적 지식을 필요로 하고 제어이론 및 설계과정이 복잡한 것으로 인식돼 우리나라에서는 그다지 많은 관심을 끌지 못하고 있는 것 같다. 그러나, 응용사례에서 알 수 있는 것처럼 그 응용대상이 광범위하고, 또한 고성능의 제어목적을 달성하기 위해 필요한 제어기법으로 자리잡아가고 있으므로 보다 더한 관심을 기울일 필요가 있을 것으로 사료된다.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.999-1010
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• 2003

Uninterrupted power supply has become indispensable during the maintenance task of active electric power lines as a result of today's highly information-oriented society and increasing demand of electric utilities. This maintenance task has the risk of electric shock and the danger of falling from high place. Therefore it is necessary to realize an autonomous robot system using electro-hydraulic manipulators because hydraulic manipulators have the advantage of electric insulation and power/mass density. Meanwhile an electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to realize not only stable contact work but also accurate force control for the autonomous assembly tasks using hydraulic manipulators. In this paper, the robust force control of a 6-link electro-hydraulic manipulator system used in the real maintenance task of active electric lines is examined in detail. A nominal model for the system is obtained from experimental frequency responses of the system, and the deviation of the manipulator system from the nominal model is derived by a multiplicative uncertainty. Robust disturbance observers for force control are designed using this information in an H$\_$$\infty$/ framework, and implemented on the two different setups. Experimental results show that highly robust force tracking by a 6-link electro-hydraulic manipulator could be achieved even if the stiffness of environment and the shape of wall change.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.9
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• pp.846-852
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• 2013

In this paper, the authors propose a new approach to control problem of the marine vessels which are moored or controlled by actuators. The vessel control problem in the specified area is called a DPS (Dynamic Positioning System). The main objective of this paper is to obtain more useful control design method for DPS. In this problem, a complicate fact is control allocation which is a numerical method for distributing the control signal to the controlled system. For this, many results have been given and verified by other researchers using two individual processes. It means that the controller design and control allocation design process are carried out individually. In this paper, the authors give more sophisticated design solution on this issue. In which the controller design and control allocation problem are unified by a robust controller design problem. In other word, the stability of the closed-loop system, control performance and allocation problem are unified by an LMI (Linear Matrix Inequality) constraint based on $H_2/H_{\infty}$ mixed design framework. The usefulness of proposed approach is verified by simulation with a supply vessel model and found works well.

• Smart Structures and Systems
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• v.15 no.4
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• pp.1041-1062
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• 2015

In this paper a method of finding optimal positions for piezoelectric actuators and sensors on different structures is presented. The genetic algorithm and multi-objective genetic algorithm are selected for optimization and $H_{\infty}$ norm is defined as a cost function for the optimization process. To optimize the placement concerning the selected modes simultaneously, the multi-objective genetic algorithm is used. The optimization is investigated for two different structures: a cantilever beam and a simply supported plate. Vibrating structures are controlled in a closed loop with feedback gains, which are obtained using optimal LQ control strategy. Finally, output of a structure with optimized placement is compared with the output of the structure with an arbitrary, non-optimal placement of piezoelectric patches.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2723-2725
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• 2005

In this paper, a robust $H{\infty}$ stabilization problem to a uncertain discrete-time nonlinear systems with time-delay via fuzzy static output feedback is investigated. The Takagi-Sugeno (T-S) fuzzy model is employed to represent an uncertain nonlinear systems with time-delayed state. Then parallel distributed compensation technique is used for designing of the robust fuzzy controller. Using a single Lyapunov function, the globally asymptotic stability and disturbance attenuation of the closed-loop fuzzy control system are discussed. Sufficient conditions for the existence of robust $H{\infty}$ controllers are given in terms of linear matrix inequalities via similarity transform and congruence transform technique.

• Journal of applied mathematics & informatics
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• v.20 no.1_2
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• pp.513-522
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• 2006

This paper considers a robust output feedback $H\infty$ controller design method for singular systems with time-varying delay in state and parameter uncertainty in system matrix by an LMI approach and observer based technique, which can be solved efficiently by convex optimization. The sufficient condition for the existence of controller and the controller design method are presented by strict LMI(linear matrix inequality) approach. Since the obtained condition can be expressed as an LMI form, all variables including feedback gain and observer gain can be calculated simultaneously by Schur complement and changes of variables.