• 조명전기설비학회논문지
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• 제19권1호
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• pp.70-79
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• 2005

본 논문은 축소차원 상태방정식을 사용한 전차원 관측기를 이용하여 저속도 영역에서의 운전 성능 개선방법을 제안하였다. 축소차원 상태방정식을 사용한 전차원 관측기는 간단한 모터속도 및 외란토크 관측기이다. 제안한 알고리즘은 약 1.9[rpm]의 저속도에서 매우 안정적인 결과를 보였다. 모터구동 시스템에서 외란토크는 저속도 영역에서 속도제어 성능을 저하시킨다. 제안한 알고리즘은 모터속도와 외란토크를 모두 추정한다. 추정된 외란 토크는 속도제어기의 출력에 전향보상 값으로 사용되며, 그 결과 저속도 영역(1.9rpm)에서 부하토크 응답특성이 향상된 것을 확인하였다.

• 제어로봇시스템학회논문지
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• 제14권8호
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• pp.856-864
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• 2008

This paper describes a vehicle low speed driving assistant (VLDA) system that is composed of laser scanner. This vehicle is designed for following lead vehicle (LV) without driver's operation. The system is made up several component systems that are based on unmanned ground vehicle (UGV). Each component system is applied to use advanced safety vehicle developed to complete UGV system. VLDA system was divided into vehicle control system and obstacle detecting system. The obstacle detecting system calculate distance and angle of LV and transmit these data to vehicle control system using front, left and right laser scanners. Vehicle control system makes vehicle control values such as steering angle, acceleration and brake position and control vehicle's movement with steering, acceleration and brake actuators. In this research, we designed VLDA system like as low speed cruise control system and test it on real road environments.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.133-139
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• 2011

In this paper, Based on Two-dimensional Flow Theory, adopting quasi-orthogonal method and point-by-point integration method to design the impeller of the low specific speed centrifugal pump by code, and using RANS (Reynolds Averaged N-S) Equation with a standard k-${\varepsilon}$ two-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the impeller of the low specific speed pump. An analysis of the influences of the blade profile on velocity distributions, pressure distributions and pump performance and the investigation of the flow regulation pattern in the impeller of the centrifugal pump are presented. And the result shows that this method can be used as a new way in low speed centrifugal pump impeller design.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권10호
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• pp.708-711
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• 2000

Sensorless PMSM is much studied for the industrial applications and home appliances because a mechanical sensor reduce reliability and increase cost. Most of sensorless algorithms are based on motor equations, and so the magnitude of phase voltage and current should be exactly obtained. However, the inverter output voltage applied to PMSM has relatively large error in the low speed range, and a relatively poor response is shown in the low speed range. This paper investigates the improved performance of sensorless PMSM in the low speed range. This paper proposes the error reduction of inverter output voltage which is realized through the variable link voltage. The proposed algorithm is verified through simulation and experiment.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권4호
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• pp.429-435
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• 2013

This paper proposes a sensorless speed control based on a novel extension of the torque producing flux (active flux) observer for the surface mounted permanent magnet synchronous machines (SPMSM) without additional high frequency signal injection. From the estimated torque producing flux, the rotor position and speed can be calculated at low speed due to their independency. Therefore, no rotor position sensor is required. Two approaches of the torque producing flux observer are presented and compared. The results show the stability and robustness of the expansion of the torque producing flux observer at low speed for the SPMSM.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.670-674
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• 2016

The control performance of hybrid PWM inverter using a phase current measurement is presented in this paper. The hybrid PWM technique consists of space vector pulse width modulation (SVPWM) and six-step voltage control operation. The SVPWM is performed to reduce the harmonic components in the low speed region, and the six-step modulation is applied to increase the maximum speed of the IPMSM in the high speed region. Therefore, it is possible to obtain a great performance in both the low speed range and high speed range. However, the six-step modulation cannot be completely implemented, since the inverter that includes the lag-shunt sensing method has an immeasurable current region. In this paper, a quasi-six-step modulation using a modified voltage vector is proposed. The validity and usefulness of the proposed PWM technique is verified by MATLAB/Simulink and experimental results.

• 한국정보통신학회논문지
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• 제2권4호
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• pp.627-634
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• 1998

본 논문에서는 관성 모멘트 동정에 의해 상태관측기의 성능 및 유도전동기의 저속운전 특성을 개선하는 알고리즘을 제안하였다 저속운전 영역에서 저 분해능 엔코더를 사용하는 속도 검출법은 속도 주기내에 펄스수가 너무 적어 정확한 속도정보를 얻을 수 없다 이러한 문제점을 개선하고자 속도와 외란을 추정할 수 있는 고피나스 이론에 근거한 상태관측기를 설계하여, 외란이 제거된 제어를 수행하였다. 또한 추정된 속도와 외란의 오차를 최소화하기 위하여 전동기의 관성 모멘트를 추정하고, 관측기의 공칭 관성 린멘트를 동정하였다. 시뮬레이션과 실험결과로부터 제안된 알고리즘은 6［rpm］ 이하의 저속영역에서 과도응답 특성의 향상을 보여주었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제42권1호
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• pp.9-12
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• 2016

Objectives: In this study we evaluated heat generation during the low-speed drilling procedure without irrigation. Materials and Methods: Ten artificial bone blocks that were similar to human D1 bone were used in this study. The baseline temperature was $37.0^{\circ}C$. We drilled into 5 artificial bone blocks 60 times at the speed of 50 rpm without irrigation. As a control group, we drilled into an additional 5 artificial bone blocks 60 times at the speed of 1,500 rpm with irrigation. The temperature changes during diameter 2 mm drilling were measured using thermocouples. Results: The mean maximum temperatures during drilling were $40.9^{\circ}C$ in the test group and $39.7^{\circ}C$ in the control group. Even though a statistically significant difference existed between the two groups, the low-speed drilling did not produce overheating. Conclusion: These findings suggest that low-speed drilling without irrigation may not lead to overheating during drilling.

• 한국산업융합학회 논문집
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• 제25권3호
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• pp.379-386
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• 2022

The goal of this research is to verify a performance test system for a low speed, high torque, and harsh reducer at low cost. The reducer rotates a cooling fan with a diameter of 10 meters, in a high temperature (50℃) cooling tower in a geothermal power plant. It requires about 500 kgf·m torque and 47.75 kW power to rotate the fan at a maximum power condition. An expensive dynamometer is commonly used for performance test of a motor or a reducer. In this paper, a low cost system is developed using a hydraulic pump as a load unit to generate torque instead of a dynamometer. We accurately calculated the required power, the flow meter, and the pressure of the pump, and selected to design and optimize the system at minimal cost. The system also applied another reverse reducer and a gearbox to increase the rotational speed and to reduce the torque from the low speed and high torque target reducer. This allows low-cost systems to be built using inexpensive components. The developed system was able to successfully measure the high torque and the low rotational speed of the target reducer at high temperature.

• 한국유체기계학회 논문집
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• 제9권3호
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• pp.29-35
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• 2006

There are high expectations of improving the performance of a centrifugal pump in the range of very low specific speed which has been developed recently for the use instead of a conventional positive displacement pump. However, even though elaborated studies has been done for the pump intensively, the pump performance has not increased so much. Also, it is difficult to find detailed information from published literatures for suction performance of the very low specific speed centrifugal pump. Therefore, this study is aimed to improve the pump performance more and to make clear suction performance of the very low specific speed centrifugal pump. Recircular flow stopper is installed on the pump casing wall at the region of impeller outlet to improve the pump performance and J-Groove is also installed at the inlet of the pump casing for the purpose of suppressing occurrence of cavitation as well as improving pump performance. The result suggests that the simultaneous improvement of pump performance and suction performance of the very low specific speed centrifugal pump is possible by adopting optimum configuration of the recirculation flow stopper and J-Groove.