• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.456-460
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• 1996

A nonlinear control scheme for preventing limit cycle due to the nonlinearity of themulti-step bang-bang actuator in mechanical position control systems is proposed. A linearized model, SIDF, fora multi-step bang-bang actuator is introduced to compensate the nonlinearity of the multi-step bang-bang actuator. Using that model, a $H_{\infty}$robust controller for position control systms with a bang-bang actuator is proposed by loop shaping tecniques with normalized coprime factorization stabilization to address the robustness. The proposed scheme needs a smaller deadband as a result of compensating the nonlinearity of the bang-bang actuator. A single-axis servo system is served in order to verify the proposed control scheme experimentally. Experimental results show that the controller can satisfy the special intersts, silent contact switching of the actuator.r.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.242-249
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• 2001

In this study, a methodology of synchronous control has been developed that can is applied to position synchronization of a two-axes driving system such as overhead crane. The synchronous error is caused by model uncertainties and torque load at each axis. To overcome these problems, the synchronous control system has been composed of two disturbance observers to calculate the torque disturbance and one synchronous controller to eliminate synchronous error. By considering model uncertainties of each axis, the synchronous controller has been designed using H(sub)$\infty$ control theory. The effectiveness of the proposed method has been verified through simulation.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.34.2-34
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• 2001

There are many control methods guaranteeing the robustness of systems. Among them, H$\infty$ control, sliding mode control and disturbance observer have been used widely. Especially, disturbance observer(DOB) is one of the most popular methods because it is easy to apply and the cost to pay is low due to its simplicity. Conventional DOB utilizes output signal as a feedback signal. But in Optical Disk Drive(ODD) systems, the Position Error Signal(PES) is the only available one. So conventional DOB is not applicable. If we use error signal in stead of output signal, another form of DOB is made. We call it as Error based Disturbance Observer(EDOB). We show in this paper the difference between two systems, namely conventional DOB system and the EDOB system, and also show the effectiveness of EDOB through experiment.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.22.5-22
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• 2001

Robust control of a GFR composite beam with a distributed PVDF sensor and piezo-ceramic actuator is presented En this paper. Modal analysis method and modal coordinates are introduced to obtain the state educations of the structural system. 1st and 2nd natural frequencies are considered In the modeling, because robust control theory which is robustness to structured uncertainty is adopted to suppress the vibration. If the controllers designed by H$\^$$\infty$/ theory do not satisfy control performance, it is improved by ${\mu}$-synthesis method with D-K Iteration so that the ${\mu}$-controller based on the structured singular value satisfies the nominal performance and robust performance.

• 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.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.12
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• pp.41-49
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• 1997

This paper deals with the attitude control of a self-made VTOL vehicle which is round shape and has four fans and motors. Although hovering mechanisms are suitable for field work at a mountainous region or a building site etc., it is known that modeling the structure of the plant is quite difficult due to its unstable or uncertain characteristics. So, a robust controller is requried in order to cope with these uncertainties. WE first model the structure of the plant under the actual hovering setting and then determine the uncertainty of the acquired mathematical model by using system identification method as exactly as possible. We adopt the $H^{\infty}$ theory as a control algorithm because of its availability, and the structure of two-degree-of-freedom is used as a basic feedback control system to improve the transient response of the plant. Finally, we show the appropriateness of the designed controller through simulations and experiments. That is, the proposed VTOL system is able to maintain its roubust performance in spite of parameter variations and existing disturbances..

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.100-109
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• 1997

Parameters in the internal combustion engines are variable depending on the operating points. Therefore, it is necessary to compensate for the uncertainties. Form this point of view, this paper gives a controller design method and a robust stability condition by LMI approach for engine torque control which satisfies the gives H$\infty$ control performance in the presence of physical parameter perturbations. To the end, the robustness of the system in the presence of perturbation is guaranteed in the all engine operating regions. Its effectiveness is demonstrated by simulation.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.342-344
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• 2006

The modem enormous electric power system has made power system analysis much more complex and difficult. For effective analysis of the power system, model reduction and aggregation is required. In this paper, a new aggregation method is presented to aggregate the coherent generators in the large scale power system while matching the power flow. In order to demonstrate the effects of this aggregation method, it is applied to a small scale power system. A multi-variable control technique of $H_{\infty}$ control is also applied to enhance the dynamic stability of the aggregated power system.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.976-979
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• 1996

Teleoperation is the extension of a person's sensing and manipulation capability to a remote location. Teleoperators generally can be modeled as linear transfer function indecently including modeling uncertainty. Modeling uncertainties can make the system unstable and its performance poor. Thus I'm studying about a design framework for a bilateral controller of teleoperator systems with modeling uncertainties. In this paper, a method based on the H$_{\infty}$-optimal control and .mu.-synthesis frameworks are introduced to design a controller for the teleoperator that achieves stability and performance in the presence of the modeling uncertainties..ties.inties.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.395-398
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• 2000

The method of Variable Structure Control (VSC) design of windmill power systems is proposed. In the design of sliding mode control, we use Riccati equations arising in linear H$\^$$\infty$/ control to decide a stable sliding surface. Then the reachability to the sliding surface is realized by designing a nonlinear controller for the windmill power system. The capability of the proposed controller to damp out the oscillations of power and the robustness with respect to the system parameter variations and model errors are evaluated in the simulation study.