• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권4호
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• pp.185-192
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• 2001

In SRM drive, the ON·OFF angles of each phase switch should be accurately controlled in order to control the torque and speed stably. The accuracy of the switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor, that are used to provide the information of the rotor position and to control the SRM power circuit, respectively. However, as the speed increases, the amount of the switching angle deviation from the preset values is also increased. Therefore, the low cost encoder suitable for the practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple digital logic circuit is also presented in this paper, As a result, a stable high speed SRM drive can be achieved by the high resolution switching angle control and it is verified from the experiments that the proposed encoder the logic controller can be a powerful candidate for the practical low cost SRM drive.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.151-154
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• 2001

Shape memory alloy (SMA) has demonstrated its potentials for various smart structure applications. SMA wires undergo a reversible phase transformation from martensite to austenite as temperature increases. This transformation leads to shape recovery and associated recovery strains. If SMA actuators are embedded off the neutral surface and are oriented in arbitrary angles with respect to a beam axis, then the beam bends and twists due to the coupling effects of recovery strains activated. In this study, the bending and twisting of a SMA/Composite beam were controlled by both electric resistive heating and passive elastic tailoring. 3-dimensional finite element formulations were derived and validated to analyze the responses of the SMA/Composite beam. Numerical results show that the shape of the SMA/Composite beam can be controlled by judicious choices of control temperatures, SMA angles, and elastic tailoring.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.190-198
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• 2002

In switched reluctance motor(SRM) drive, it is necessary to synchronize the stator phase excitation with the rotor position. Therefore the rotor position information is an essential. Usually optical encoders or resolvers are used to provide the rotor position information. These sensors are expensive and are not suitable for high speed operation. In general, the accuracy of the switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor. But the region of high speed, switching angles are fluctuated back and forth from the preset values, witch are cause by the sampling period of the microprocessor. Therefore, the low cost linear encoder suitable for the practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple digital logic circuit is also presented in this paper It is verified from the experiments that the proposed encoder and logic controller can be a powerful candidate for the practical low cost SRM drive.

• Journal of Advanced Marine Engineering and Technology
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• 제28권3호
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• pp.413-422
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• 2004

The flow characteristic in the wake around a circular cylinder with tripping wires, which was set in constant distance, was experimentally investigated in the uniform flow, Re=2.92$\times10^4$. The measurement of velocity vector and pressure distribution are carried out various angles of tripping wires in the range of $50^(\circ)$ to $80^(\circ)$ with $10^(\circ)$ interval. The results show that velocity profiles and pressure distributions are different with angles of tripping wires. The drag of the circular cylinder was decreased about 60% maximum when tripping wires' angle was $50^(\circ)$. The lowest reduction of the velocity and wake width was occurred by coanda effect when the angle was $60^(\circ)$, and the vortex shedding periodicity become rare at the same time.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.77-82
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• 2003

In end milling process, undeformed chip thickness and cutting force vary periodically with phase change of the tool. Recently, a model has been proposed to simulate the shear and friction characteristics of an up-end milling process in terms of the equivalent oblique cutting to this. In the current study, the varying undeformed chip thickness and the cutting forces in a down-end milling process have been replaced with the equivalent ones of oblique cutting. And, the down-end milling characteristics of SM45C has been compared with that of the up-end milling previously presented with different helix angles.

• Journal of Advanced Marine Engineering and Technology
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• 제24권3호
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• pp.58-69
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• 2000

An experimental study was conducted to investigate the influence of the spinning control cylinders which was set on the surface of a fixed circular cylinder in uniform flow, $Re=1.24\times10^4$. The measurements of velocity vectors and pressure distributions are carried out in various spin parameters and angles of spinning control cylinder. The results show that velocity profiles and pressure distributions are different with angles of control cylinder and spin parameters. When the control cylinder angle is $100^{\circ}$, there is more effect in increasing the velocity and the pressure distribution than other cases. In this case, the vortex shedding frequency was increased as increasing spin parameter.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1371-1376
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• 1990

The paper presents a method of constructing simple fuzzy control rules for the determination of stabilizing signals of automatic voltage regulator and governor, which are controllers of electric power systems. Fuzzy control rules are simplified by considering a coordinate transformation with the rotation angle .theta. on the phase plane, and by expanding the range of membership functions. Also, two rotation angles .theta. $_{1}$ and .theta. $_{2}$ are selected for the linearizable region and the nonlinear one of the system, respectively. Here, .theta. $_{1}$ is chosen by the pole assignment method, and .theta. $_{2}$ by a performance index. Fuzzy inference is applied to the connection of two rotation angles .theta. $_{1}$ and .theta. $_{1}$ by regarding the distance from the desired equilibrium point as a variable of condition parts. The control effect is demonstrated by an application of the proposed method to one-machine infinite-bus power system.

• 제어로봇시스템학회논문지
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• 제7권2호
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• pp.117-124
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• 2001

In a SRM drive, the on/off angles of each phase switch should be accurately controlled in order to control to torque and speed in a stable way, The accuracy of the switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor. However, as the speed increase, the amount of the switching angle deviation from the preset values is also increased by the sampling period of the microprocessor. Therefore, a low cost encoder suitable for a practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple digital logic circuit is also presented in this paper. It is verified from the experiments that the proposed encoder and logic controller can be a powerful candidate a the practical low cost SRM drive.

• Journal of Power Electronics
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• 제15권1호
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• pp.227-234
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• 2015

This paper presents the application of bee colony optimization (BCO) to obtain the optimal switching angles for single phase PWM AC choppers. The optimal switching angles are found in the region of 0-${\pi}$ based on the asymmetrical PWM technique. This PWM process results in improvements of the total harmonic distortion of the output voltage and in the input power factor. Simulation and experimental results are compared with the conventional PWM to verify the performance of the proposed PWM process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.101-104
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• 1987

The problem considered is that of calculating the angles of arrival of a multimoded signal at an antenna array from simultaneous measurements of the amplitude and the phase of the signal in each element of the array. The method of wavefront analysis 15 applied to a 4-element direction finder of the Adcock type. A simulated problem is constructed with the aid of suitable computer programs developed here.