• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.760-769
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• 2006

This paper proposes an autopilot system using a fuzzy PID controller to satisfy performances required for the automatic navigation of ships under various marine circumstances. The existing autopilot system using a PD type controller has difficulties in eliminating a steady-state error and compensating nonlinear characteristics of ships. The autopilot system using the proposed fuzzy PID controller has a self-tuning ability, an ability to compensate nonlinear characteristics, and an ability to turn at constant angular velocity. Therefore. it can naturally make a steady-state error zero, compensate nonlinear dynamic effect of ships, have an adaptability to parameter variation owing to shallow water effect, and have an ability to turn ship's course rapidly without overshoot through procedures of acceleration, constant, and deceleration of angular velocity for large course-changing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.346-350
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• 2004

In Blu-ray(BD) optical system, as a short laser wavelength of laser diode and thin cover layer thickness of' disc, the proper adjustment of spherical aberration should be performed. Considering thin cover layer' thickness and tolerance variation of disc in BD optical system, spherical aberration in BD format is mort: serious than CDㆍDVD format Especially, in dual-layer disc, to compensate the aberration at each layer, optical component should be moved finely in the way of optical path. In this study, 1 -axis moving actuator was introduced as the method of compensating the spherical aberration, and the mechanism of the system was described. Finally, its effect on optical system will be mentioned.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.544-551
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• 2000

In this paper, 3-phase hybrid series active power filter for compensate current harmonics, voltage drop and unbalanced voltage in the network presented. The proposed system is implemented with a space vector modulation voltage source inverter and a high pass filter connected in parallel to the power system. Here the load is six-pulses thyristor rectifier. The phase angle detected in order to generation reference voltage at load terminal is synchronized with the positive sequence component of the unbalanced source by using symmetrical component transformation. The proposed system has an function harmonic isolation between source and load, voltage regulation, and unbalance compensation. Therefore, what the power system is improved quality, the source current is maintained as a nearly sinusoidal waveform and the load voltage is regulated with a rated voltage regardless of the source variation condition. To verify the validity of the proposed compensating system, the computer simulation and experiment are carried out.

• Journal of Biosystems Engineering
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• v.21 no.2
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• pp.155-166
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• 1996

A direct injection sprayer was designed using the concepts of injection mixing and total flow control, flowrate-based system compensating for the variation of forwarding speed. A metered rate, proportionally to the actual diluent flow rate, of a tracer chemical was injected directly into the diluent stream. The injection of chemical may improve the precision and safety of chemical application process. The control system was evaluated for the variables of the control interval, tolerances and sensitivities of flow regulation valve and injection pump. Performance of the system was assessed as that the response time of flow rate, response time of injection rate, absolute steady state error, and the coefficient of variance(C.V.) of concentration were 8.5 and -0.53 seconds, 0.067 lpm(0.8%) and 3.15%, respectively, at optimal parameters of control interval of 1.0 sec, fast sensitivity of flow regulation valve, medium sensitivity of injection pump and medium tolerance of flow rate. Performance of the system can be improved by increasing the sensitivity of flow regulating valve and employing a high resolution velocimeter, such as Doppler radar.

• IE interfaces
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• v.12 no.1
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• pp.150-157
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• 1999

Mini-Mill process has been recently in operation at Pohang steel company, which enables more flexible steel coil production on customer demands. The effects of process parameters in Mini-Mill process need to be analyzed not only to make the process stable but also to improve product quality. This work aims to develop a regression model of Mini-Mill process using accumulated product data such that the process parameter effects on product tensile strength may be analyzed. The analysis shows that tensile strength is influenced mainly by the amount of components such as carbon, manganese, silicon, and sulfur. The effect of temperature is shown to be small. It is concluded that control of the components is much more responsible for both meeting the target and reducing the variation of the product tensile strength. Heat treatment is more useful in compensating tensile strength variations due to thickness differences and improving workability and other quality characteristics. More work is necessary for establishing regression expressions of the process that is reliable and accurate enough to dispense with the off-line inspection of the product tensile strength.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.22-23
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• 2006

A new current-driving pixel circuit for active-matrix organic light-emitting diodes (AMOLEDs), composed of four organic thin-film transistors (OTFTs) and one capacitor, is proposed using a current scaling method. Designing pixel circuits with OTFTs has many problems due to the instability of the OTFT parameters with still unknown characteristics of the material. Despite the problems in using OTFTs to drive the pixel circuit, our work could be set as a goal for future OTFT development. The simulation results show enhanced linearity between input data and OLEO luminescence at low current levels as well as successfully compensating the variation of the OTFTs, such as the threshold voltage and mobility.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.2
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• pp.93-99
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• 1989

This paper describes Sinusoidal Wave-Variable Voltage Variable Fequency (SW-VVVF) system for the high efficiency drive of a 3-phase induction motor. SW-VVVF system consists of a 3-phase 24-pulse converter and a SPWM inverter. The converter with additional 2 tap diode circuits in interphase reactor reduces harmonics in input current. The SPWM inverter consists of an improved PLL system and a V/F controller, which reduces harmonics in output current and performs a high efficiency algorithm by maintaining a constant slip frequency and compensating for the velocity variation of the induction motor with the change of load. Therefore, this system reduces harmonics in input and output currents, and also can drive an induction motor with high efficiency in an economical way. We have proved its utility through experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.65-68
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• 2001

In the vector control methods of induction motor, the stator current is divided into the flux and torque component current. By controlling these components respectively, the methods control independently flux and torque as in the DC motor and improve the control effects. To apply the vector control methods, the position of the rotor current is identified. The indirect vector control use the parameters of the machine to identify the position of rotor flux. But due to the temperature rise during machine operation, the variation of rotor resistance degrades the vector control. To solve the problem, the q-axis is aligned to reference frame without phase difference by comparing the real flux component with the reference flux component. Then to compensate the slip, PI controller is used. The proposed method keeps a constant slip by compensating the gain of direct slip frequency when the rotor resistance of induction motor varies. To prove the validations of the proposed algorithm in the paper, computer simulations is executed.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.159-162
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• 2001

This paper is proposed an efficiency optimization operation algorithm for synchronous reluctance motor (SynRM) using current phase angle control technique. The SynRM has to controlled with the optimal current phase angles with load and operation speed variation, to obtain high efficiency over the wide speed ranges. An efficiency optimization condition in SynRM which minimizes the copper and iron losses is derived based on the equivalent circuit model of the machine. The objective of the efficiency optimization control algorithm compensating the optimum current angle, is to seek a combination of d and q-axis current components which provides minimum losses at a certain operating point in steady state. The usefulness of the proposed efficiency optimization control is verified through vector-controlled inverter system with the SynRM.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1041-1043
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• 1993

A robust position control scheme for a Brushless Direct Drive Motor(BLDDM) is presented. To obtain the robustness under the load variation, a Variable Structure Controller(VSC) is used. However, the VSC has a chattering problem and require the full state informations. To overcome this problem, in this paper, the sliding mode observer is used for compensating the load disturbance and estimating the motor velocity. As a result, the VSC for a BLDDM posision control is designed by using only position measurment and the chattering problem is greatly reduced. To show the validaty of the proposed scheme, the simulation study is carried out.