• International Journal of Control, Automation, and Systems
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• v.2 no.4
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• pp.475-484
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• 2004

In this paper, we present a dynamic output-feedback receding horizon $H_{\infty}$controller for linear discrete-time systems with disturbance. The controller is obtained numerically from the finite horizon output-feedback $H_{\infty}$optimization problem, which is, in fact, hardly solved analytically. Under a matrix inequality condition on the terminal weighting matrix, the monotonic decreasing property of the cost is shown. This property guarantees both the closed-loop stability and the $H_{\infty}$norm bound. Then, we extend the proposed design method to a reference tracking problem and a problem for time-varying systems. Numerical examples are given to illustrate the performance of the proposed controller.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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• pp.83-88
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• 2015

Due to low cost and high reliability, Brushless DC (BLDC) motors have been widely used in control applications such as robotics, aerospace and automobile. In the high performance control systems, it is very important to maintain the desired speed even in the face of parameter uncertainties, modeling errors, and disturbance signals. In this paper, we present an $H_{\infty}$ controller for the speed control of BLDC motors to achieve better performance of disturbance rejection. In particular, we discuss how to reduce an initial peaks of control input in the proposed $H_{\infty}$ controller. Some experimental results are provided to establish the effectiveness of the proposed method.

• Proceedings of the KIEE Conference
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• 2004.05a
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• pp.7-9
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• 2004

This paper provides an observer-based $H_{\infty}$ controller design method for singular systems with and without time-varying delay by just one LMI condition. The sufficient condition for the existence of controller and the controller design method are presented by perfect LMI (linear matrix inequality) approach. The design procedure involves solving an LMI. The observer-based $H_{\infty}$ controller in the existing results can be constructed from the coupled two or more conditions while the proposed controller design method can be obtained from an LMI condition, which can be solved efficiently by convex optimization. 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. An example is given to illustrate the results.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.864-867
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• 1990

In this paper, a state space solution to the discete time H$_{\infty}$ control problem is presented. It is shown that there exist LQ game problem corresponding to H$_{\infty}$ control problems and the H$_{\infty}$ controller can be obtained by solving the LQ game problem. Explicit state space formulae are given for the state feedback H$_{\infty}$ controller and output feedback H$_{\infty}$ controllers.lers. state feedback $H_{\infty}$ controller and output feedback $H_{\infty}$ controllers.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.65.2-65
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• 2001

There are not only lots of controllers such as UMC(Unit Master Controller), BMC(Boiler Master Controller), Fuel Flow controller, Air flow controller, Feed water flow controller, S/H R/H Temperature controller and so on, but also compensation controller such as BTU compensator, Fuel/Water ratio controller and O2 Co controller to take automatic control in the super critical once through boiler. It is important to make complete automation of boiler to use the compensation controller like BTU compensator. For example, In case of some boiler condition, operator has to change combustion parameter for changing the coal, on the contrary BTU compensator can calculate set value of the fuel flow and reset the fuel flow demand by itself. This paper shows us the logic and instruction regarding compensation controller of boiler that can be operated automatically.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.316-321
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• 2007

[ $H{\infty}$ ] controller, which shows robustness for disturbances and noises, can not be used in the case of uncertain system parameters. Even if the $H{\infty}$ controller can be designed for the parameter uncertain system, its performance can be deteriorated. Therefore, in this paper, the robustness of $H{\infty}$ controller is improved by using the SMC(Sliding Mode Control). The LMI based $H{\infty}$ controller is designed first and then SMC controller is added.

• 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.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2584-2586
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• 2000

A drum level control is one of the most important control systems in thermal power plant. The control objective of drum level of boiler in thermal power plant is to maintain drum level at constant set-point regardless of disturbance such as main steam flow. The implemented drum level controller is the cascade PI controller. The important factor in drum level controller is the parameters of two PI controllers. The tuning of PI controller parameter is tedious and time-consuming job. In this paper, the relay feedback Ziegler - Nichols tuning method extended to auto-tune cascade PI drum level controller. Finally, the simulation result using boiler model in Power Plant shows the validity of auto-tuned cascade PI controller.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.248-252
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• 2002

In this study, a synchronous controller which can be applied to two-axes position synchronization has been developed. The synchronous control system based on coupling structure has been composed of speed and synchronous controller. The speed controller has been designed to fellow speed reference. And the synchronous controller has been designed in the view point of accurate synchronization and robust stability by $H_{\infty}$ approach. The effectiveness of the designed synchronous controller has been demonstrated by experiment.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1187-1200
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• 2002

This paper is concerned with the design or an LMI (Linear Matrix Inequality) -based H$\infty$ controller for a line of sight (LOS) stabilization system and with its robustness performance. The linearization of the system is necessary to analyze various nonlinear characteristics, but the linearization entails modeling uncertainties which reduce its performance. In addition, the stability of the LOS can be adversely affected by angular velocity disturbances while the vehicle is moving. As the vehicle accelerates, all the factors that are Ignored and simplified for the linearization tend to Inhibit the performance of the system. The robustness in the face of these uncertainties needs to be assured. This paper employs H$\infty$ control theory to address these problems and the LMI method to provide a suitable controller with minimal constraints for the system. Even though the system matrix does not have a full rank, the proposed method makes it possible to design a H$\infty$ controller and to deal with R and S matrices for reducing the system order. It can be also shown that the proposed robust controller has a better disturbance attenuation and tracking performance. The LMI method is also used to enhance the applicability of the proposed reduced-order H$\infty$ controller for the system given. The LMI-based H$\infty$ controller has superior disturbance attenuation and reference input tracking performance, compared with that of the conventional controller under real disturbances.