• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.219-224
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• 1988

A decentralised computational procedure is proposed for the optimal feedback gain matrix of large-scale discrete-time systems with time-delays. The constant feedback gain matrix is computed from the optimal state and input trajectries obtained hierarchically by the interaction prediction method. All the calculation in this approach are done off-line. The resulting gains are optimal for all the initial conditions. The interaction prediction method is applied to time-delay large-scale systems with general structures by extending the dimensions of coupling matices. A numerical exampie illustrates the algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.871-876
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• 1989

We propose a new algorithm to obtain the output feedback controller, which contains one dynamic element, for power system generators. The performance criterion of this controller is the integral of quadratic form of output differences between reference model and controlled system. with this criterion, we can easily compute the output feedback gains using Astrom's algorithm for the integral calculation of quadratic form.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.837-842
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• 1988

We propose a new algorithm to obtain the output feedback controller for power system generators. The performance criterion of this controller is the integral of quadratic form of output differences between reference model and controlled system. With this criterion, we can easily compute the output feedback gains using Astrom's algorithm for the integral calculation of quadratic form. Simulations on a one machine infinite bus system shows the effectiveness of this approach.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1733-1739
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• 1997

An ultra-compact milimeter-wave broadband MMIC amplifier was designed using a direct-coupled topology combined with optimum feedback design. Significant reductionin the chip size was possible by employing the direct-coupled topology. Bias resistors required for the direct-coupled topology were also used as feedback elements. Feedback was optimized for millimeter-wave frequencies using reactive elements. The fabricated MMIC amplifier was realized in a chip size of 0.8mm$^{[-992]}$ and showed gains higher than 8 dB from 12 to 44 GHz. An output power of 30mW was achieved at 44 GHz with a drain efficiency of 10%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8A
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• pp.612-617
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• 2012

Two phase control (PC) schemes using limited feedback are proposed for multiple-input single-output (MISO) systems. One PC scheme cophases channel gains with respect to the first transmit antenna channel gain, and the other PC scheme cophases channel gains by positioning all the channel gains into a fixed sector. We analyze the combined channel gain for both PC schemes, and find that the PC scheme that cophases with respect to the first transmit antenna channel gain provides 1.2 dB power gain over an orthogonal space-time block code (OSTBC) when the number of transmit antennas is four and the number of feedback bits is three.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2427-2433
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• 2015

This paper presents an observer-based robust controller for constant reference tracking of linear time invariant systems with polytopic model uncertainties. To this end, this paper not only designs a robust integral controller gain but also suggests how to determine the robust observer gain and the observer model used in the observer. Since the observer model selection is not obvious due to the polytopic uncertainties, particular attention needs to be paid to that. This paper computes the robust controller and observer gains first. Then, the observer model is selected in a way that the whole closedloop is stable and LMIs are used in the middle of choosing the gains and observer model. Simulation examples show that the proposed observer-based feedback control successfully achieves robust reference tracking.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.295-298
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• 1996

In this paper, a self-tuning optimal control algorithm is proposed to retain the optimal performance of an active suspension system, when the vehicle has some time varying parameters and parameter uncertainties. We consider a 2 DOF time-varying quarter car model which has the parameter variation of sprung mass, suspension spring constant and suspension damping constant. Instead of solving algebraic riccati equation on line, we propose a neural network approach as an alternative. The optimal feedback gains obtained from the off line computation, according to parameter variations, are used as the neural network training data. When the active suspension system is on, the parameters are identified by the recursive least square method and the trained neural network controller designer finds the proper optimal feedback gains. The simulation results are represented and discussed.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.844-847
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• 1996

This paper describes the servo position control for the 2-axis positioning table the servo controller consists of conventional feedback loops, disturbance observer. To reduce the contour error, which occurs in the multi-dimensions machines, cross-coupled controller(CCC) is suggested. A weak point of the CCC is their low effectiveness in dealing with arbitrary nonlinear contour such as circles and parabolas. This paper introduces a new nonlinear CCC that is based on control gains that vary during the contour movement The gains of CCC and adjusted in real time according to the shape of nonlinear contour. The feedback controller based on the disturbance observer compensated for external disturbance, plant uncertainty and bad effectiveness by friction model. Suggested servo controller which improve the contouring accuracy, apply to the 2-axis system. Simulation results on 2-axis table verify the effectiveness of the proposed servo controller.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.4
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• pp.377-384
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• 2007

This paper studies on the relation between linearization methods and controller gains in the looper ILQ(lnverse Linear Quadratic optimal control) system for hot strip finishing mills. Firstly, two linear models arc respectively derived by a linearization method using Taylor's series expansion and a static state feedback linearization method, respectively, and the linear models are compared with the nonlinear model. Secondly, the looper servo controllers are respectively designed on the basis of two linearization models. Finally, the relation between the performances of two ILQ servo controllers and the linearization methods, and the structures and control gains of two controllers are evaluated by a computer simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.5
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• pp.561-566
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• 1998

This paper presents an algebraic approach to optimal control for time invariant continuous system using STWS(single term Walsh series). In optimal control, it is well known that the design problem with quadratic performance criteria often involves the determination of time-varying feedback gain matrix by solving the matrix nonlinear Riccati equation and of command signal by solving the integral equation, which makes design procedure quite difficult. Therefore, in order to resolve this problem, this paper is introduced to STWS. In this paper, the time-varying feedback gains and command signals are determined by piecewise constant gains which can be easily obtained from algebraic equation using STWS.