• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.366-369
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• 1994

In this paper, reduced-order $H_{\infty}$ robust controller is designed for the drum-type boiler system. From the known nonlinear dynamic model, a linearized multivariable model is obtained. To reduce order of robust controller, observer-based proper $H_{\infty}$ compensator is designed. The designed controller has robust property against the influence of sensor noise, system parameter variation and model uncertainty. A good Performance of the designed controller is shown by simulation.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1213-1216
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• 1996

This paper describes a precise temperature control method for refrigerating and air conditioning systems. The control technique is based on the optimal servo control design method and the control algorithm is implemented on a personal computer. To control the precise temperature, two actuators such as an inverter for the compressor speed control and a stepping motor for regulating the expansion valve are used. The superheat and evaporator temperatures are chosen as the system output. So a multivariable system which has two inputs and two outputs to be controlled. The complicative model is identified by using an ARX(Auto Regressive eXogenous) model and the controller is designed by using the Matlab software.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.11
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• pp.928-934
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• 2002

A natural way to cope with fault tolerant control (FTC) problems is to modify the control parameters according to an online identification of the system parameters when a fault occurs. However. due to not only difficulties Inherent to the online multivariable identification in closed-loop systems, such as modeling errors, noise or the lack of excitation signals, but also long time requirement to identify the post-fault system and implemeutation of control problems during the identification process, we propose an alternative approach based on the observer-based fault detection and isolation (FDI) and model reference adaptive control (MRAC). The proposed robust fault diagnosis method is based on a bank of observers. We also propose a model reference adaptive control with changeable reference models according to the occurred faults. Simulation results of a flight control example show the validity and applicability of the proposed algorithms.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.45-48
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• 1990

This paper deals with the control strategy for constant voltage, constant frequency (CVCF) generation of doubly-fed Induction generator. As induction machine is a nonlinear and multivariable machine, so, the influential factors for CVCF generation of induction generator are the magnitude of output voltage, load current and its power factor, slip of the machine, etc. To get appropriate control scheme and to research the effect of its parameters, the control equation of induction machine is derived and tested. The derived condition is very useful for the CVCF control of the machine and for determing the characteristics of the system. The simulation results show that magnetizing reactance and rotor resistance is a very important parameter in this control system.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.349-354
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• 2011

This paper addresses the trajectory tracking problem for ship berthing using sliding mode technique. With significant potential advantages: insensitivity to plant nonlinearities, parameter variations, remarkable stability and performance robustness with environmental disturbances, the multivariable sliding modes controller is proposed for solving trajectory tracking of ship in harbor area. In this study, the ship position and heading angle are simultaneously tracked to guarantees that the ship follows a given path (geometric task) with desired velocities (dynamic task). The stability of the proposed control law is proved based on Lyapunov theory. The proposed approach has been simulated on a computer model of a supply vessel with good results.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.9
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• pp.750-754
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• 2005

This paper deals with the design problem of multivariable PID controllers guaranteeing the closed-loop system stability and a prescribed $H_\infty$ norm bound constraint. We reduce the problem to the static output feedback stabilization problem. We derive a necessary and sufficient condition f3r the existence of PID controllers and we give an explicit formula of PID controllers. We also give an existence condition of PID controllers guaranteeing a prescribed decay rate. Finally, we give an LMI-based design algorithm, together with a numerical design example.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.191-196
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• 1993

Since the welding process is complex and highly nonlinear, it is very difficult to accurately model the process for real-time control. In this paper, a discrete-time transfer function matrix model for gas metal arc welding process is proposed. Although this linearized model is valid only around the operating point of interest, the adaptation mechanism employed in the control system render this model useful over a wide operating range. A multivariable one-step-ahead adaptive control strategy combined with a recursive least-squares method for on-line parameter estimation is implemented in order to achieve the desired weld bead geometries. Command following and disturbance rejection properties of the adaptive control system for both SISO and MIMO cases are investigated by simulation and experiment.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1995.10b
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• pp.25-28
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• 1995

A Practical application of self-tuning fuzzy controller to a multi-input multi-output complex system of a vehicle engine is investigated. The ovjective is to design a controller to improve the transient performance in torque and RPM mode changes. For the performance improvement in the multivariable comples system, the self-tuning function of internal parameters is essential and practical. The measured output variables using different control schemes are compared the advanteges of the self-tuning fuzzy logic controller are better output performances and the effectiveness in the controller design using many parameters.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.3
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• pp.255-257
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• 2009

The robust stabilization problem of a multivariable uncertain system with a polytopic model is considered. A PI-type $H_{\infty}$ controller with a low pass filter is used for robust stabilization and noise rejection. The problem is reduced to an LMI optimization problem. A sufficient condition for the existence of the PI controller is derived in terms of LMIs. The PI gain matrices are parameterized by using the solution matrices to the existence conditions. Finally, a numerical design example is given.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.12
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• pp.1208-1211
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• 2010

We propose a variable structure control design method for a class of multivariable uncertain state-delayed systems which can be represented by polytopic models. In terms of LMIs, we derive a sufficient condition for the existence of a linear sliding surface guaranteeing the asymptotic stability of the sliding mode dynamics. We parameterize the sliding surface by using the solution of the LMI existence condition. We also give a switching feedback control strategy guaranteeing stable sliding mode. By using a numerical example, we show that our method supplements the existing results and it can be better than the existing results.