• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.246-251
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• 1990

A fuzzy control scheme has been proposed for a supercritical extraction process which has attracted much attention recently as a new separation technology. Based on the manual operation experience, three control pairs between manipulated and output variables are selected first and then seven membership functions are defined for control error and time rate of the error, respectively for each control pair, resulting in forty nine Fuzzy control rules. In addition to these, the membership functions are defined in two steps (coarse and fine) to enhance control performance. Fuzzy inference is performed using MAX-MTN composition rule and defuzzified control output is calculated based on center of gravity method. The prosed Fuzzy control scheme has been assessed through numerical simulation. As a result, the proposed scheme shows good control performance comparable with that by INA(inverse nyquist array) which usually requires complicated design procedure.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1701-1704
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• 2002

In this paper, we investigate the effect of power control step size on the performance of the SIC scheme in DS/CDMA systems. We investigate the average power control iteration and its standard deviation and evaluate the outage performance for several different values of power control step size. Because the SIC scheme requires fine control in the received signal power, the better outage performance is obtained fer the smaller power control step size. However, the smaller power control step size requires larger amount of power control iteration in order to make the power control converge to the steady state. Under the simulated environment, the proper power control step size is about 0.3-0.4dB from both convergence speed of power control algorithm and outage performance points of view.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.256-261
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• 2002

In this paper, it is presented a new scheme of adaptive-neuro control system to implement real-time control of robot manipulator. Unlike the well-established theory for the adaptive control of linear systems, there exists relatively little general theory for the adaptive control of nonlinear systems. Adaptive control technique is essential for providing a stable and robust performance for application of robot control. The proposed neuro control algorithm is one of learning a model based error back-propagation scheme using Lyapunov stability analysis method. Through simulation, the proposed adaptive-neuro control scheme is proved to be a efficient control technique for real-time control of robot system using DSPs.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.443-448
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• 1998

As the strip caster system that produces a regular steel plate can be considered as a complicate nonlinear multi-variable system, it is not easy to obtain an effective control system. One way to overcome the difficulties is to apply the intelligent neuro-fuzzy fusion approach in developing the control scheme. The neuro-fuzzy control scheme possesses several distinct advantages, including the fact that it doesn't need the exact mathematical modeling of controlled plant and can provided some robustness in the control scheme. In this paper, an intelligent neuro-fuzzy for the stripe caster system will be proposed. The effectiveness of the proposed scheme will be demonstrated by computer simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.7
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• pp.1214-1229
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• 2011

Power control is a key technique in spectrum underlay cognitive network to guarantee the interference temperature limit of the primary users (PUs) and the quality of service of the secondary users (SUs). In this paper, a robust power control scheme via link gain pricing with $H_{\infty}$ estimator is proposed. The scheme guarantees the interference temperature of the PUs through operating in the network-centric manner, and keeps the fairness between the SUs through link gain pricing. Furthermore, the $H_{\infty}$ filter is also used in the proposed scheme to estimate the channel variation, and thus the power control scheme is robust to the severe channel fading. Plenty of simulations are taken, and prove its superior robust performance against the channel fading, and its effectiveness in guaranteeing the interference temperature limit of the PUs.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.1-7
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• 2003

In this paper, we discuss the control scheme on active compliance control of flexible manipulators. The active compliance control scheme is extended from the scheme for rigid manipulators. To illustrate the validity of the proposed control scheme, we show experimental results for the case when the end-effector is not moving and when it is moving while applying force. Although flexible manipulators show some problems of stability yet it is clear from these results that flexible manipulators are more effective to reduce damage of environment because of link flexibility than rigid ones.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.2
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• pp.87-97
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• 2010

A fault tolerant satellite attitude control scheme with a modified iterative learning law is proposed for dealing with actuator faults. The actuator fault is modeled to reflect the degradation of actuation effectiveness, and the solar array-induced disturbance is considered as an external disturbance. To estimate the magnitudes of the actuator fault and the external disturbance, a modified iterative learning law using only the information associated with the state error is applied. Stability analysis is performed to obtain the gain matrices of the modified iterative learning law using the Lyapunov theorem. The proposed fault tolerant control scheme is applied to the rest-to-rest maneuver of a large satellite system, and numerical simulations are performed to verify the performance of the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.952-960
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• 1996

In this paper, a new overload control scheme is proposed for a control system in ATM switching system. The proposed control scheme includes a counter that conunts the number of accepted calls and is decreased at cach D time interval. In overload condition of call processor, the control scheme detects over load condition when the counter value reaches a certain threshold value. Under overload condition, processor utilization is measured and the value of the D is updataed according to the difference between measured processor utilization and target utilization. A new call is accepted accepted only if the value of the counter is less than the threshold value. In overflow condition of cell traffic, accept probability of new call is reduced exponetially according to the elapsed time. The results of simulation show that the proposed overload contorl scheme maintains the target utilization very well under the various processor overload conditions and reduces the cell loss probability under the cell overflow conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.47-51
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• 1992

Automatic detection of tool breakage during NC machining is a key issue not only for improving productivity but to implement the unattended manufacturing system. In this paper, we develop a vibration sensor-based tool breakage detection system for NC milling processes. The system obtains the time-domain vibration signal from the sensor attached on the spindle bracket of our CNC machine and declares tool failures through the on-line monitoring schemes. For on-line detection, our approach is to use the PSC(statistical process control) methods being increasingly used for on-line process control. The main thrust of this paper is to propose and compare the performance of SPC methods including : a) X-bar control scheme, b) S control scheme, c)EWMA (exponentially weighted moving average) scheme, and d) AEWMA (adaptive exponentially weighted moving average) scheme. The performance of the control schemes are compared in terms of the type 1 and 2 error calculated from the experiment data.

• Journal of Power Electronics
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• v.7 no.1
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• pp.72-80
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• 2007

Voltage sags are one of the most frequently occurring power quality problems challenging power systems today. The Unified Power Quality Conditioner (UPQC) is one of the major custom power solutions that are capable of mitigating the effect of supply voltage sags at the load or Point of Common Coupling (PCC). A UPQC-Q employs a control method in which the series compensator injects a voltage that leads the supply current by $90^{\circ}C$ so that the series compensator at steady state consumes no active power. However, the UPQC-Q has the disadvantage that its series compensator needs to be overrated. Thus it cannot offer effective compensation. This paper proposes a new control scheme for the UPQC-Q that offers minimum power injection. The proposed minimum power injection method takes into consideration the limits on the rated voltage capacity of the series compensator and its control scheme. The validity of the proposed control scheme is investigated through simulation and experimental results.