• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.37-38
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• 2010

For MHz-class high frequency inverter in wireless power transfer applications, the voltage/current surges can be occurred in power stage when driving on the inverter. And also, the high-frequency oscillations can be produced at a high switching frequency due to the parasitic elements. The voltage and current stresses of the switching devices lead to the switching losses. The efficiency of the high frequency inverter will be reduced. And the inverter circuit with the sudden voltage and current fluctuations also generates the noise such as the EMI. Zero voltage, zero current switching technique can be used to reduce the switching loss and the noise. The high power density and high efficiency can be obtained. In this paper, the high-frequency inverter for short-range wireless power transfer applications was discussed. The feasible inverter circuit is analyzed in the circuit operating characteristics and the results are verified by the simulation.

• 한국컴퓨터정보학회논문지
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• 제23권2호
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• pp.1-7
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• 2018

The adaptive optics for compensating for optical wavefront distortion due to atmospheric turbulence has recently been used in systems that improve beam quality by eliminating the aberrations of high power laser beam wavefront. However, unseen-mode, which can not be measured in the wavefront sensor, increases the instability of the laser beam wavefront compensator on the adaptive optics system. As a method for improving such instability, a mathematical method for limiting the number of singular values is used when generating the command matrix involved in generation of the drive command of the wavefront compensator. In the past, however, we have relied solely on experimental methods to determine the limiting range of the singular values. In this paper, we propose a criterion for determining the limiting range of the singular values using the driving characteristics and the correlation technique of the wavefront compensator's actuators and have proved its performance experimentally.

• 대한전기학회논문지
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• 제43권5호
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• pp.747-752
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• 1994

The switched reluctance motor has high efficiency over a wide range of speed and torque. However the switched reluctance motor exhibit comparatively low efficiency in the chopped excitation which produces additional inverter losses. This paper examines the optimal efficiency operation using choppingless excitation under the changed supply voltage. The excitation is designed to produce the required torque and speed satisfying the optimal efficiency in a nonlinear switched reluctance motor. The optimal algorithm is applied to 119 operation points which are chosen over the full range of driving torque and speed. The result in this paper indicate the improved efficiency comparing to the efficiency obtained by both switched and chopped excitataions under a fixed supply voltage.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.186-187
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• 2007

In this work, a temperature stable PWM(Pulse width modulation) circuit is proposed. The designed PWM circuit has a temperature dependent current source and a temperature independent voltage to compensate electrical characteristics with operating temperature. The variation of driving current is from about 4% to -6% in the temperature range $0^{\circ}C\;to\;70^{\circ}C$ compared to the current at the room temperature. The variation of bandgap voltage reference is from about 1.3% to -0.2% with temperature when the supply voltage is 3.3 volts. From simulation results, the variation of output pulse width is less than from 0.86% to -0.38% in the temperature range $0^{\circ}C\;to\;70^{\circ}C$.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.139-141
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• 2019

본 논문은 무인이동체를 위한 관제시스템을 사용 하기위해 최근 다양한 연구가 진행되어 왔던 LoRa망 적용을 제안한다. LoRa(Long Range)는 최대 30km정도의 넓은 커버리지를 가지고 있으며, 대규모 저전력 장거리 무선통신이 특징이다. 이미 LoRa는 다양한 산업에 적용되어 연구되어 오고 있다. 또한 LoRa망을 활용하여 무인이동체들의 관제시스템에 적용시켜 다양한 기능에 대한 연구를 제안한다.

• 유공압시스템학회논문집
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• 제4권1호
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• pp.18-24
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• 2007

The continuously variable transmission (CVT) of which speed ratio can change continuously in a fixed range has the benefits of low fuel consumption and exhaust gas because it enables the engine of a vehicle to operate in a high efficiency range regardless of vehicle speed. The speed ratio of belt type CVT is controlled by adjusting line pressure. The one of the line pressure control methods, mechanical-hydraulic control is usually adopting VDT's control method, in which the secondary solenoid valve has two functions both a regulator and a line pressure controller. However, this control method could not show the high performance of CVT with optimal driving capability because of the limitation of simple control algorithm, and it could not gain market share sufficiently in spite of the advantage of CVT with low fuel consumption. On the other hand, the electro-hydraulic control method gives the enhancement of power performance and low fuel consumption by implementing various driving mode using the proportional control or PWM control. The key of CVT technique is to develop a control algorithm of the electro-hydraulic solenoid valve in order to implement the speed ratio efficiently. In this paper, the line pressure control algorithm is proposed and the hydraulic system is controlled using metal belt type CVT test rig and the embedded ECU platform.

• IEIE Transactions on Smart Processing and Computing
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• 제2권5호
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• pp.310-316
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• 2013

This paper reports a sinusoidal $180^{\circ}$ drive for a permanent magnet (PM) brushless motor employing automatic angle compensator to suppress the driving loss during the wide-range load operation. The proposed drive of the sinusoidal $180^{\circ}$ PM Brushless motor reduced the amplitude of the 3-phase current by compensating for the lead-angle of the fundamental waves of the 3-phase PWM signal. The conventional lead-angle method was implemented using the fixed angle or memorized table, whereas the proposed method was automatically compensated by calculating the angle of the current and voltage signal. The algorithm of the proposed method was verified in a 30 W PM brushless motor system using a PSIM simulator. The efficiency of the conventional method was decreased 90 % to 60 %, whereas that of proposed method maintained approximately 85 % when the load shift was 0 to $0.02N{\cdot}m$. Using an FPGA prototype, the proposed method was evaluated experimentally in a 30 W PM brushless motor system. The proposed method maintained the minimum phase RMS current and 79 % of the motor efficiency under 0 to $0.09N{\cdot}m$ load conditions. The proposed PM brushless motor driving method is suitable for a variety of applications with a wide range of load conditions.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.523-530
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• 2006

A rotordynamic analysis was performed with a dry vacuum pump, which is a major equipment in modern semiconductor and LCD manufacturing processes. The system is composed of screw rotors, lobes picking air, helical gears, driving motor, and support rolling element hearings of rotors and motor. The driving motor-screw rotor system has a rated speed of 6,300rpm, and was modeled utilizing a rotordynamic FE method for analysis, which was verified through the results of its 3-D finite element model. As loadings on the bearings due to the gear action were significant in the system considered, each resultant bearing load was calculated determinately and indeterminately by considering the generalized forces of the gear action as veil as the rotor itself. Each resultant hearing loading was used in calculating each stiffness of rolling element bearings. Design goals are to achieve wide separation margins of critical speeds and favorable unbalance responses of the rotor in the operating range. Then, a complex rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds, whirl natural frequencies and mode shapes, and unbalance responses under various unbalance locations. Results show that the entire system is well designed in the operating range. In addition, the procedure of rotordynamic analysis for dry vacuum pump rotor-bearing system was proposed and established.

• 한국산학기술학회논문지
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• 제14권10호
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• pp.4679-4684
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• 2013

기존 내연기관에 비해 전기자동차가 가지는 한계 중 하나는 에너지 밀도가 상대적으로 낮은 배터리로 인한 짧은 주행거리이며, 겨울철 실내 난방을 위하여 전기 히터 사용 시, 전기 소모량이 30%이상 증가하는 문제가 발생한다. 본 연구에서는 전기 히터보다 에너지 효율이 우수한 히트펌프를 이용하여 난방 시, 전기 자동차의 주행성능 변화를 조사하였다. 일차원 해석 프로그램인 AMESim Software를 이용하여 전기자동차의 구동시스템 및 히트펌프의 해석모델을 개발하였고, 해석 결과 전기 히터를 히트펌프로 대체하면, 배터리 소모량이 약 50% 감소하여 그 만큼의 주행거리를 증가시킬 수 있는 것으로 나타났다. 본 연구 결과는 전기자동차 난방을 위한 히트펌프의 장점을 입증하였으며, 향후 전기 자동차 난방 대책의 비전을 제시하는데 기여할 것으로 사료된다.

• 한국유체기계학회 논문집
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• 제10권3호
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• pp.47-54
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• 2007

A rotordynamic analysis was performed with a dry vacuum pump, which is a major equipment in modem semiconductor and LCD manufacturing processes. The system is composed of screw rotors, lobes picking air, helical gears, driving motor, and support rolling element bearings of rotors and motor. The driving motor-screw rotor system has a rated speed of 6,300rpm, and was modeled utilizing a rotordynamic FE method for analysis, which was verified through the results of its 3-D finite element model. As loadings on the bearings due to the gear action were significant in the system considered, each resultant bearing load was calculated determinately and indeterminately by considering the generalized forces of the gear action as well as the rotor itself. Each resultant bearing loading was used in calculating each stiffness of rolling element bearings. Design goals are to achieve wide separation margins of critical speeds and favorable unbalance responses of the rotor in the operating range. Then, a complex rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds, whirl natural frequencies and mode shapes, and unbalance responses under various unbalance locations. Results show that the entire system is well designed in the operating range. In addition, the procedure of rotordynamic analysis for dry vacuum pump rotor-bearing system was proposed and established.