• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.285-287
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• 2001

To obtain a high performance in a vector controlled induction machine, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantages with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations.

• Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.36-41
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• 2009

Quad-rotor is one kind of a rotorcraft in Unmanned Aerial Vehicle (UAV), which consists of four rotors in total and fixed-pitch blades located at the four corners. This vehicle is emerging as popular platform for UAV research due to the simplicity of its construction, the ability of hovering and the vertical take-off and landing (VTOL) capability, etc. Because of those specific capabilities, this vehicle can be applied to many fields: search and rescue, mobile sensor networks, fire observation, etc. However a quad-rotor is much affected by the disturbance due to the characteristics of structure. So this vehicle needs attitude control for stabilizing. In this paper, we design the control law for automatic stabilization. The PID controller is used to control a brushless DC motor. And an accelerometer is used to measure the roll and pitch angles of a quad-rotor.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.2
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• pp.146-153
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• 2005

In a permanent magnet brushless dc motor, cogging torque is produced by the magnetic attraction between the rotor mounted permanent magnets and the stator teeth. This always produces a pulsating torque ripple resulting in vibration and acoustic noise, which is detrimental to the motor performance. This paper deals with the analytical prediction of cogging torque and the various cogging torque minimization techniques as applied to a permanent magnet brushless dc motor.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.3
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• pp.207-213
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• 2000

This paper introduces a high-performance speed control system based on artificial neural networks(ANN) to estimate unknown parameters of a DC servo motor. The goal of this research is to keep the rotor speed of the DC servo motor to follow an arbitrary selected trajectory. In detail, the aim is to obtain accurate trajectory control of the speed, specially when the motor and load parameters are unknown. By using an artificial neural network, we can acquire unknown nonlinear dynamics of the motor and the load. A trained neural network identifier combined with a reference model can be used to achieve the trajectory control. The performance of the identification and the control algorithm are evaluated through the simulation and experiment of nonlinear dynamics of the motor and the load using a typical DC servo motor model.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.205-213
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• 2014

A wind generator (WG) maximum power point tracking (MPPT) system is presented here. It comprises of a variable-speed wind generator, a high-efficiency boost-type dc/dc converter and a control unit. The advantages of the aimed system are that it does not call for the knowledge of the wind speed or the optimal power characteristics and that it operates at a variable speed, thus providing high efficiency. The WG operates at variable speed and thus suffers lower stress on the shafts and gears compared to constant-speed systems. It results in a better exploitation of the available wind energy, especially in the low wind-speed range of 2.5-4.5 m/s. It does not depend on the WG wind and rotor-speed ratings or the dc/dc converter power rating. Higher reliability, lower complexity and cost, and less mechanical stress of the WG. It can be applied to battery-charging applications.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.119-122
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• 2001

본 논문은 브러시리스 DC 모터 드라이브에서 위치센서를 제거하기 위해, 측정한 상전압 및 상전류로부터 쇄교자속과 쇄교자속의 미분간에 의해 속도를 구하고 이를 이용하여 위치를 추정하는 새로운 센서리스 구동방식을 제안한다 이러한 센서리스 구동알고리즘은 ${\alpha}-{\beta}$ 기준축을 이용하여 구현하였다. 구동시스템을 구현하기 위한 제어기는 고속연산이 가능하면서도 저가인 고정소수점 연산 DSP인 TMS320F241을 채택하였다. 제안된 알고리즘은 그 원리가 간단하고 우수한 제어특성을 나타냄으로써 실제적인 브러시리스 DC 전동기의 센서리스 구동을 위한 훌륭한 대안이 될 수 있을 것이다.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.641-643
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• 2000

Because of high torque and easiness of speed control, Direct Current(DC) motors are used long time. But, its applications are limited in circumstance and performance, since they contained brush and commutator. The commutation characteristic gives effect to life and performance of DC motor. Naturally, the commutation characteristic analysis is strongly required. In this paper, With the result of finite element analysis. The inductance is calculated each rotor position and applied to the voltage equations coupled with commutation equation. The time derivative term in the differential equation is solved in time difference method. This algorithm was applied to 2-pole shunt DC motor. We considered commutation characteristic by changing contact resistance between brush and commutator segment.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.200-204
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• 1998

In this paper, a mathematical model of Brushless DC machine fed by pwm inverter is developed. Dynamic and steady state characteristics of Brushless DC motor is simulated and analyzed: electromagnetic torque, speed, phase voltage, and current. In mathematical modeling, the shaft transformation referencing rotor frame from to "a,b,c" three phase frame to "d,g" two phase frame is described.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.385-387
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• 1999

Brushless DC Motors are widely used because of their high power ratio and easy control. But the brushless DC Motors need rotor Position- and speed- sensor such as encoder, resolver and hall sensor. The position sensor has present several disadvantages from the standpoint of drive cost, machine size and reliability. Hall sensors are used generally because of low cost but their operating temperature is limited up to $75^{\circ}C$ because of sensitivity of temperature. Now a day many research projects are on the development of sensorless brushless DC motors to correct these disadvantages. In this paper, characteristics such as starting, change of speed and load of a sensorless brushless DC motor are investigated.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.191-197
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• 2005

In the fabrication process of Fe-based amorphous alloy powder cores by pulverization of the melt-spun ribbons and cold compaction, the effects of powder preparation method on the magnetic & electric properties, powder shapes and microstructure of cores have been investigated. The powder cores made by using rotor mill showed low effective permeability as compared to the cores prepared by ball milling. However the frequency dependence and quality factor properties were superior in the case of rotor-milling. Further the powders prepared by rotor mill had homogeneous and round shapes through strong shearing in the sieve ring, while the ball milled powders were inhomogeneous and relatively small. The lower permeability of the powder cores fabricated with rotor mill was considered to be due to the high internal stress occurred by very intensive shearing. Moreover the powder cores produced by rotor-milling showed lower core loss and good frequency dependence of effective permeability possibly due to the higher electrical insulation between magnetic particles. The dc bias property of the powder cores made by rotor-milling was better than the one by ball-milling.