• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.1919-1921
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• 1998

In this paper, a control method for field weakening region of induction machine drive which is based on indirect field oriented control was implemented. Also, application method of direct field oriented control in the field weakening region using maximum torque control methods which is adaptable for parking facilities was studied. The implemented method which is based on direct field oriented control method ensures the full utilization of the output torque capability of the machine over the conventional 1/${\omega}_r$ method. And machine drive system can obtain the robustness to motor parameter variation.

• 유공압시스템학회논문집
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• 제1권4호
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• pp.1-8
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• 2004

The optimum design parameters of several hydraulic systems are obtained using the complex method that is one kind of constrained direct search method. First, the parameters of lead-lag controller of the direct drive servovalve is designed using the complex method to satisfy the steady-state error requirement. Second, the optimum locating point of hydraulic cylinder Is determined to minimize the cylinder force in the operation range of rotational sluice gate. For the third application case, the optimum piston area of hydraulic cylinder is determined to minimize the man power to elevate the manually operated sluice gate.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권10호
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• pp.637-645
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• 2000

This study was represented the improvement of the flexible position control for linear motion of hybrid type linear pulse motor(HLPM). The driving method used a minute 125 microstep drive instead of full step drive method. The digital control method was applied to the PI control for more stable position control, at this time the PI control parameters have gained by a Ziegler-Nichols turning method. The loop transfer function of control system was combined with both motor transfer function and digital PI control equation. Such, the proper for digital PI control system is verified to through the simulation and experimental result of the stability step response and bode plot with proper gain and phase margin.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
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• pp.51-55
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• 2011

In this paper, the optimized doping condition of crystalline silicon solar cells with 156 ${\times}$ 156 mm2 area was studied. To optimize the drive-in condition in the doping process, the other conditions except drive-in temperature and time were fixed. After etching 7 ${\mu}m$ of the surface to form the pyramidal structure, the silicon nitride deposited by the PECVD had 75~80 nm thickness and 2 to 2.1 for a refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in $400-425-450-550-850^{\circ}C$ five-zone temperature conditions to make the ohmic contact. Drive-in temperature was changed in range of $828^{\circ}C$ to $860^{\circ}C$ and time was from 3 min to 40 min. The sheet resistance of wafer was fixed to avoid its effect on solar cell. The solar cell fabricated with various conditions showed the similar conversion efficiency of 17.4%. This experimental result showed the drive-in temperatures and times little influence on solar cell characteristics.

• 한국정보통신학회논문지
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• 제20권7호
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• pp.1290-1295
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• 2016

최근 모바일 인터넷 이용률이 급증하면서 인터넷 이용자의 웹 브라우저를 통한 사회 공학적 또는 드라이브 바이 다운로드 방식으로 악성코드 유포 공격이 확산되고 있다. 현재 드라이브 바이 다운로드 공격 방어 초점은 최종 다운로드 사이트 및 유포 경로에 초점을 두어 진행되어 왔으나 공격 초기 악성코드를 주입하는 인젝션 사이트에 대한 특성 탐지 및 차단에 대해서는 충분히 연구되지 않았다. 본 논문에서는 이러한 악성 코드 다운로드 공격에 대한 방어메커니즘 향상을 목적으로, 악성코드 다운로드의 핵심 근원지인 인젝션 사이트를 탐지하는 방안에 대해서 연구한다. 결과적으로 악성코드의 확산을 방지하기 위해 다운로드 공격의 최종 사이트를 탐지 및 차단하는 현재의 URL 블랙리스트 기법에 추가하여, 악성코드를 주입하는 인젝션 사이트를 탐지 특징을 추출 하는 방안을 제시한다. 또한 URL 블랙리스트 기반의 접근법과 비교하여 악성코드 감염률을 효율적으로 최소화 할 수 있는 방안임을 보인다.

• Journal of Power Electronics
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• 제13권2호
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• pp.250-255
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• 2013

This paper proposes an optimal current distribution method of dual-rotor brushless DC machines (DR-BLDCMs) which have inner and outer surface-mounted permanent-magnet rotors. The DR-BLDCM has high power density and high torque density compare to the conventional single rotor BLDCM. To drive the DR-BLDCM, dual 3-phase PWM inverters are required to excite the currents of a dual stator of the DR-BLDCM and an optimal current distribution algorithm is also needed to enhance the system efficiency. In this paper, the copper loss and the switching loss of a DR-BLDCM drive system are analyzed according to the motor parameters and the switching frequency. Moreover, the optimal current distribution method is proposed to minimize the total electrical loss. The validity of the proposed method was verified through several experiments.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권2호
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• pp.207-214
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• 2014

If two or more Permanent Magnet Synchronous Motors (PMSM) can be controlled by one inverter, a train can be driven by less energy than the present Induction Motor (IM) drive system. First, this paper proposes a method for simulating the movement of wheels and a vehicle to develop a control method. Next, a method is presented for controlling two or more PMSMs by one inverter.

• KSTLE International Journal
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• 제5권2호
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• pp.52-56
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• 2004

The hard disk drive performance depends strongly on air bearing characterisitcs of the head slider. The objective of the slider design is to provide accurate positioning of the magnetic read/write element at the very small height above the disk. Application of the numerical methods is required due to complexity of the air bearing surface of the slider. The Boundary-Fitted Coordinate System Divergence Formulation method can be used for calculation of pressure distribution in the case of steep film thickness gradients. In the present work, the interpolating functions used in the expression for the Couette flow are modified in order to improve the solution characteristics in the extremely high compressibility number region. The advantages of the modified method are demonstrated on example of the flat skewed slider. Finally, the modi.ed method is applied to analysis of the static characteristics of the femto-slider. The analysis results indicate the effect of the silder's air bearing surface crown on the flying height and the pitching angle in steady state position.

• 한국멀티미디어학회논문지
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• 제21권9호
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• pp.1068-1075
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• 2018

We propose a method for driving loudspeakers from class D audio power amplifiers in current mode, instead of in conventional voltage mode, which was impossible with the feedback circuitry. Unlike analog audio amplifiers, Class D audio power amplifiers have signal delay between the input and output signals, which makes it difficult to apply the feedback circuitry for current-mode driving. The idea of the pre-distortion scheme used for the compensation of the non-linearity of RF power amplifiers is adapted to remedy the impedance variation effect of the loudspeakers for current driving. The method uses the speaker model for the pre-distorter to compensate for the speaker impedance variation with frequency. The simulation and test results confirms the validity of the proposed method.

• Journal of Power Electronics
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• 제2권1호
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• pp.55-66
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• 2002

A new on-line dead-time compensation method for a permanent magnet (PM) synchronous motor drive is proposed. Using a simple disturbance observer without any additional circuit and off-line experimental measurement, disturbance voltages in the synchronous reference dq frame caused by the dead time and non-ideal switching characteristics of power devices are estimated in an on-line manner and fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Simulations and experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method.