• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.437-442
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• 1996

The paper presents a design method of dynamic positioning control system for floating platform with rotatable and retractable thruster using $H_{\infty}$control technique. The norm band of uncertaintyis captured by multiplicative perturbation between nominalmodel and reduced order model. A controller robust to theuncertainty is designed applying $H_{\infty}$synthesis. The control law satisfying robust stability and nominal performance condition is determined through the mixed sensitivity approach. The evaluation for the resultant controller obtained by $H_{\infty}$synthesis is done through simulations of the closed loop system. The results of $H_{\infty}$synthesis are compared to those of the traditional LQ synthesis method. method.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.350-353
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• 1994

This paper presents a method to calculate the characteristic root areas and loci band of control systems with uncertainties. First, equations of boundary curves of root areas in the case of additive and multiplicative perturbation are derived. Then, an algorithm for the calculation of the array of closed curves is presented. When the upper bound of the absolute values of frequency responses for the uncertain part, is also frequency-dependent, the frequency-dependent, terms are included in the characteristic equation of the nominal system. This lead to the boundary equations of the root, areas for control systems with frequency-dependent uncertainty. Numerical examples of the control systems with multiplicative perturbations including frequency-dependent terms are presented to verify this calculation method. Finally, its applications to the design of robust control systems, e.g., passive adaptive control systems are also discussed.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.153-161
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• 1996

This paper presents a design method of dynamic positioning control system for floating platform with rotatable and retractable thruster using $H_{\infty}$ control technique. The norm band of uncertainty is captured by multiplicative perturbation between nominal model and reduced order model. A controller robust to the uncertainty is designed applying $H_{\infty}$ synthesis. The control law satisfying robust stabillity and nominal performance condition is determined through the mixed sensitivity approach. The evaluation for the resultant controller obtained by $H_{\infty}$ synthesis is done through simulations of the closed loop system. The results of $H_{\infty}$ synthesis are compared to those of the traditional LQ synthesis method.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.487-495
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• 2015

This paper proposes a new robust decentralized power oscillation dampers (POD) design of doubly-fed induction generator (DFIG) wind turbine for damping of low frequency electromechanical oscillations in an interconnected power system. The POD structure is based on the practical $2^{nd}$-order lead/lag compensator with single input. Without exact mathematical model, the inverse output multiplicative perturbation is applied to represent system uncertainties such as system parameters variation, various loading conditions etc. The parameters optimization of decentralized PODs is carried out so that the stabilizing performance and robust stability margin against system uncertainties are guaranteed. The improved firefly algorithm is applied to tune the optimal POD parameters automatically. Simulation study in two-area four-machine interconnected system shows that the proposed robust POD is much superior to the conventional POD in terms of stabilizing effect and robustness.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.84-90
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• 1995

The magnetic levitation system has great advantages, such as little friction, no lubrication no noise and so on. The magnetic levitation system need a stabilizing controller because it is a unstable system in natural. This paper presents the robust stabilizing controller design of the magnetic levitation system. The controller which is designed in this paper by $H_{infty}$ control theory is robust servo controller which has zero offset in spite of the model uncertainties. The validity of controller was investigater through the response simulation. In the future, we will use the result of this study at the actual magnetic levitation system.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.3
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• pp.144-153
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• 1996

The magnetic levitation system has many advantages, such as little friction, no lubrication, no noise and so on. For this reason, the magnetic levitation system is utilized in the magnetic bearing of high-speed rotor. The method to obtain magnetic force is both the repulsive suspension method and the attraction suspension method need a stabilizing controller because it is a unstable system in natural. This paper presents the design of robust stabilizing servo controller in spite of being the model uncertainties in the magnetic levitation system by $\textit{H}_{\infty}$ control theory using the free parameter. And we investigated the validity of a designed controller through results of the simulation and the actual experiment.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.62-69
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• 1999

This paper presents a design method of dynamic positioning control system(DPS) for floating Platform with rotatable and retractable thrusters using H$\infty$ servo control design method. The norm band of uncertainty is captured by multiplicative perturbation between nominal model and reduced order model. A controller robust to the uncertainty is designed applying H$\infty$ synthesis. The control law satisfying robust stability and nominal performance condition is determined through the mixed sensitivity approach. The control algorithm was evaluated on the basis of computer simulation for a proposed DPS design method and experiments was carried out with an image processing method for measurement of DPS position in a water tank The results of overall experiments show that proposed control method will be good to keep at a specified position. And they are compared with the experimental results by LQG synthesis and H$\infty$ optimal control design method.