• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.356-364
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• 2013

This paper presents a tracking gain-up controller design method to control effectively the vibration of tracking actuator caused by external shocks and remaining velocity after seek control. A pole placement constraint is considered to assure a desired transient response against the vibration of tracking actuator. A loop gain-up constraint is introduced to hold the tracking gain-up loop gain and control bandwidth within allowable bounds. The pole placement constraint is expressed by a matrix inequality and the loop gain-up constraint is considered as an objective function so that genetic algorithm can be applied. Finally, a tracking gain-up controller is obtained by integrating a genetic algorithm with LMI design approach. The proposed tracking gain-up controller design method is applied to the track-following system of a DVD recording device and its effectiveness is evaluated through the experimental results.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.7
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• pp.619-624
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• 2011

This paper presents a controller design method for a robust control problem with multiple constraints using genetic algorithms and LMI design method. A robust $H_{\infty}$ constraint with loop shaping and pole placement is used to address disturbance attenuation with error limits and desired transient specifications, in spite of the plant uncertainties and disturbances. In addition, a loop gain constraint is considered so as not to enlarge the loop gain unnecessarily. The robust $H_{\infty}$ constraint and pole placement constraint can be expressed in terms of two matrix inequalities and the loop gain constraint can be considered as an objective function so that genetic algorithms can be applied. Accordingly, a robust controller can be obtained by integrating genetic algorithms with LMI approach. The proposed controller design method is applied to a track-following system of an optical disk drive and is evaluated through simulation results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.3
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• pp.275-283
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• 2012

This paper presents a design method of a robust tracking controller satisfying multiple constraints using genetic algorithm. A robust $H_{\infty}$ constraint with loop shaping is used to address disturbance attenuation with error limits and a loop gain constraint is considered so as not to enlarge the tracking loop gain and bandwidth unnecessarily. The robust $H_{\infty}$ constraint is expressed by a matrix inequality and the loop gain constraint is considered as an objective function so that genetic algorithm can be applied. Finally, a robust tracking controller can be obtained by integrating genetic algorithm with LMI approach. The proposed tracking controller design method is applied to the track-following system of an optical DVD recording drive and is evaluated through the experimental results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.5
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• pp.361-368
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• 2015

This paper deals with a robust fine seek controller design problem with multiple constraints using a genetic algorithm. A robust $H\infty$ constraint is introduced to attenuate effectively velocity disturbance caused by the eccentric rotation of the disk. A weighting function is optimally selected based on the estimation of velocity disturbance and the estimated minimum velocity loop gain. A robust velocity loop constraint is considered to minimize the variances of the velocity loop gain and bandwidth against the uncertainties of fine actuator. Finally, a robust fine seek controller is obtained by solving a genetic algorithm with an LMI condition and an appropriate objective function. The proposed controller design method is applied to the fine seek control system of a DVD recording device and is evaluated through the experimental results.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.10
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• pp.988-993
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• 2009

In this paper, we deal with a tracking gain-up controller design problem to control effectively the shake of tracking actuator after a track seek. A minimum tracking gain-up open-loop gain can be calculated by estimating the shake of tracking actuator and a desired transient specification is considered to diminish effectively the shake of actuator. A tracking gain-up controller is designed by considering a robust $H_{\infty}$ control problem with a regional stability constraint. The proposed tracking gain-up controller design method is applied to the track-following system of a DVD recording device and is evaluated through the experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.376-382
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• 1986

Adaptive control constraint (ACC) is applied to a turning process to keep the cutting force constant while the cutting conditions vary. In this system, a given reference force is compared with the measured cutting force and difference is input to the controller to adjust the feed. Since it is found that the effective ACC loop gain depends on both depth-of-cut and spindle speed and thereby influence the system stability, a simple computer algorithm is built in the controller to maintain the stability of the whole system by on-line estimation of the process parameters during cutting.

• International Journal of Control, Automation, and Systems
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• v.5 no.6
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• pp.621-629
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• 2007

In the adaptive fuzzy control field for affine nonlinear systems, there are two basic configurations: direct and indirect. It is well known that the direct configuration needs more restrictions on the control gain than the indirect configuration. In general, these restrictions are difficult to check in practice where mathematical models of plant are not available. In this paper, using a simple extension of the universal approximation theorem, we show that the only required constraint on the control gain is that its sign is known. The Lyapunov synthesis approach is used to guarantee the stability and convergence of the closed loop system. Finally, examples of an inverted pendulum and a magnet levitation system demonstrate the theoretical results.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.9
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• pp.520-525
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• 2000

This paper deals with the design of H$\infty$ control for uncertain linear systems with the regional eigenvalue assignment constraint. The considered region is a disk in the left half plane and the two types of time-varying uncertainties are considered. We presents a state feedback control that minimize the L2 gain from the disturbance to the measured output as well as it guarantees that all eigenvalues of closed loop are inside a disk. The state feedback control is obtained by checking the feasibility of linear matrix inequalities (LMI's) which are numerically tractable. Finally we give an example to show the applicability and usefulness of our results.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1131-1133
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• 1996

In this paper, we consider the mixed $L_1/H_{\infty}$ problems of finding internally stabilizing controllers which minimize the peak-to-peak gain of a certain closed loop transfer function with $H_{\infty}$-norm constraint on other closed loop transfer function(or vise versa). This problem is a useful framework for designing a controller with the norm constraints upon time and frequency domain. We formulate the mixed $L_1/H_{\infty}$ problem as LMI problems by using the reachable set. This paper offers the sufficient condition for the existence of suboptimal state feedback controller, and shows that suboptimal solution can be obtained by solving a finite-dimensional convex optimization and a line search.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.15-22
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• 2006

In OFDMA system, even if the number of allocated sub-channel in mobile station varies from one to the whole sub-channel as in base station, while because of mobile station's transmit power is lower than that of base station, therefore full loading range(FLR) constraint occurs where whole sub-channel can be used and the conventional open-loop power control scheme can not be used beyond FLR. We propose a new scheme that limits the maximum sub-channel allocation number and uses power concentration gain(PCG) depending on location of mobile station, which is based on ranging in OFDMA system. Simulation results show that the proposed scheme provides solutions for optimum utilization of radio resource depending on the location of mobile station and enables open-loop power control beyond FLR without extra hardware complexity.