• 제어로봇시스템학회논문지
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• 제20권9호
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• pp.914-921
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• 2014

In this paper, an algorithm is suggested to detect an offset angle of the absolute rotor position sensor after the initial assembly of a PMSG. Unlike previous studies in a stationary state, this one is not designed to detect an electrical angle but rather the absolute position of the rotor is detected while operating the generator. Also,a position sensor, current sensors and voltage sensor were used to ensure reliability. This technique completes the detection of the sensor offset in two steps. In the first step, a zero-crossing of the EMF is measured using a voltage sensor to detect the electrical angle offset when the alternator is actuated by the engine. In the second step, a high frequency current is injected along the d-axis on-line during the control of the generation, eventually to obtain the inductance using a DFT (Discrete Fourier Transform), and then to ultimately extract the final electrical angle offset through the comparison of the inductance magnitude. The suggested algorithm was validated with PSIM simulation and, furthermore, was tested with actual experiments on a dynamometer.

• 한국소음진동공학회논문집
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• 제17권12호
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• pp.1246-1253
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• 2007

The recent issue of optical pickup actuators is to apply optical storage devices to mobile devices such as a cellular phone and PDA. It requires actuators to become smaller than conventional types. As the size becomes smaller, the magnetic force is reduced and the assembly of optical pickup actuators becomes more difficult. In addition, its dynamic characteristics are changed. In this paper, methods to improve magnetic forces and dynamic characteristics are suggested and the optimal result of the plate spring design is obtained. A diamond shape magnet and the fine pattern coil (FPC) are used to improve magnetic forces and damping elements are attached to decrease the peak magnitude of the mode instead of using structural damping, mostly for the purpose of improving the accuracy of the finite element simulation. To get more stable dynamic characteristics than conventional ones, a plate spring is applied to the optical pickup actuator and it is optimized with topology and parameter optimization to obtain the concept and the detail design, respectively.

• 전기학회논문지
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• 제64권11호
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• pp.1645-1650
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• 2015

This paper presents the 3-dimensional electromagnetic field analysis method and correction of sensor distortion that is used by a motor speed sensor. The magnetic sensors are being expanded due to lower price than the other speed sensors such as resolver and encoder. Magnetic sensor generates sine and cosine waves when the motor rotates. However, the sine and cosine signals are distorted due to magnetic noise, which makes the angle error of the sensor, generated near by the Hall element. This paper defines an optimal design variables by using the Taguchi method to minimize output distortion of the magnetic sensor and permanent magnet. To enhance reliability of the magnetic position sensor from sensitivity error, assembly amplitude mismatch and the electrical angle, 3-Dimensional electromagnetic finite element method and correction algorithm errors were performed in due of the magnetic sensor in order to improve the quality of the initial production model.

• The Journal of Advanced Prosthodontics
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• 제9권1호
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• pp.14-21
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• 2017

PURPOSE. The aim of this study was to compare the retention of mini implant overdenture by the number, the type of magnetic attachment, and the directions of applied dislodging force. MATERIALS AND METHODS. The experimental groups were designed by the number and type of magnetic attachment. Twenty samples were tested with Magden implants. Each attachment was composed of the magnet assembly in overdenture sample and the abutment keeper in a mandibular model. Dislodging forces were applied to the overdenture samples (50.0 mm/min) in 3 directions. The loading was repeated 10 times in each direction. The values of dislodging force were analyzed statistically using SPSS at 95% level of confidence. RESULTS. The retentive force of group 2 was greater than that of group 1 in both types of attachment in every direction (P < .05). Oblique retentive force of flat type magnetic attachment was higher than that of cushion type attachment in both groups (P < .05). In group 1, oblique retentive force showed the highest and anterior-posterior retentive force showed the lowest value in both attachment types (P < .05). In group 2, both types of attachment showed the lowest retentive force with anterior-posterior direction of dislodging force (P <.05). CONCLUSION. Proper retentive properties for implant overdenture were obtained, regardless of the number and type of magnetic attachment. In both types of magnetic attachment, the greater retentive force was attained with more implants. Oblique retentive force of flat type magnetic attachment was greater than that of cushion type. Among all subgroups, anterior-posterior retentive force was the lowest among three different directions of dislodging force.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권11호
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• pp.601-611
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• 2002

As resent trends in structural construction have been to build taller and larger structures than any time in the past, they have had high flexibility and low damping that can cause large vibration response under severe environmental loading such as earthquakes, winds, and mechanical excitations. The damper with mass and sqring is one aproach to safeguarding the structure against excessive vibrations. In this paper, a large capacity hybrid-type linear motor damper(LMD) was designed and fabricated for the application to the vibration control of a large building structure model. It has been designed to be able to move the damper mass, 1,500 kg up to ${\pm}250mm$ strokes at the first mode natural frequency of the building structure model, ${\pm}0.51Hz$. Linear motor is consisted of the fixed coil and the movable NdFeB permanent magnets field part. The PM field part composed magnet modules and iron yoke, is the damper mass itself, 1500kg. LMD therefore has a simplified structure and requires a few elements in the driving system, being compared with a rotary motor damper and a hydraulic damper. However, the manufacture of large PM linear actuator is difficult because of the limit of PM size and the attraction and repulsion at the assembly of PM. Therefore, large damper system is manufactured and tested for dynamic characteristics and frequency response.

• Progress in Superconductivity
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• 제14권1호
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• pp.66-70
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• 2012

Superconductor flywheel energy storage system (SFESs) is an electro-mechanical battery with high energy storage density, long life, and good environmental affinity. SFESs have been developed for application to a regenerative power of train, the storage of distributed power sources such as solar and wind power, and a power quality improvement. As superconductor bearing is completely passive, it is not necessary to control a system elaborately but accurate analysis in mechanical properties of the HTS bearing is very important for application to SFESs. Stiffness and damping properties are the main index for evaluation the capacity of HTS bearings and make it possible to adjust rotordynamic properties while operating the rotor-bearing system. The superconductor bearing consists of a stator containing single grain YBCO bulks, a ring-type permanent magnet rotor with a strong magnetic field that can reach the bulk surface, and a bearing support for assembly to SFESs frame. In this study, we investigated the stiffness and damping properties of superconductor bearings in 35 kWh SFESs. Finally, we found that 35 kWh superconductor bearing has uniform stiffness properties depend on the various orientations of rotor vibration. We discovered total damping coefficient of superconductor bearing is affected by not only magnetic damping in superconductor bulk but also external damping in bearing support. From the results, it is confirmed that the conducted evaluation can considerably improve energy storage efficiency of the SFESs, and these results can be used for the optimal capacity of superconductor bearings of the SFESs.

• 한국인터넷방송통신학회논문지
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• 제21권2호
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• pp.143-149
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• 2021

BLDC 전동기는, 영구자석의 고성능화를 비롯한 소재 기술 향상, 고집적·고기능화를 갖는 구동 IC 기술의 진보, 고점적율화 등의 조립 기술 개선 등으로 인하여 성능이 점점 좋아지고 있다. 이러한 구형파 구동 BLDC 전동기의 장점이 있으면서 보다 사용자의 요구에 대응하기 위해 구형파 구동 BLDC 영구자석 전동기 설계 및 개발, 위치검출방식 회로와 드라이버 개발에 관심이 증가하고 있다. 그러나 스위칭 손실에 의한 효율 저하 및 진동, 소음 등으로 인하여 가격적·기능적인 장점에도 불구하고 그 응용에 있어서는 다소 제한적인 실정이다. 따라서 본 논문에서는 정현파가 발생하는 Hall Effect Sensor를 사용하여 BLDC 전동기 회전자의 자속에 비례하여 정현파 신호를 만드는 위치검출 회로를 연구하여 전동기의 효율 증대, 리플 저감, 속도 및 토크 특성이 우수한 정현파 전류 구동을 구현하고자 한다.

• 한국인터넷방송통신학회논문지
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• 제21권4호
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• pp.135-141
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• 2021

산업자동화에 적합한 구형파 구동 BLDC 영구자석 전동기 설계 및 개발, 위치검출방식 회로와 드라이버 개발에 관심이 증가하고 있다. 그러나 이 전동기는 스위칭 손실에 의한 효율 저하 및 진동, 소음 등으로 인하여 가격적·기능적인 장점에도 불구하고 그 응용에 있어서는 다소 제한적인 실정이다. BLDC 모터를 설계하고 조립하는 과정에 있어 자기회로 설계의 문제 또는 조립과정상의 제품 불 균일 등으로 인하여 자극 각이 균일하지 않거나 자속분포가 왜현되는 문제가 발생하는데, 이러한 것들이 위치검출 어긋남의 원인이 되어 모터 특성을 악화시킨다. 또한 위치센서로부터 발생된 신호가 정확히 드라이버로 피드백 되어야만 정현파 구동 BLDC 시스템이 안정적으로 동작할 수 있다. 그러나 발생된 신호가 외부의 영향인 자속밀도 편차나 착자 기술에 의해 DC offset 성분이 발생하여 안정적인 위치검출을 할 수 없기에 본 연구에서는 DC offset 성분을 제거할 수 있는 제안된 회로를 연구하고자 한다.

• Smart Structures and Systems
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• 제29권5호
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• pp.661-675
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• 2022

In this paper, an electric vehicle drives with efficient control and low cost hardware using four quadrant DC converter with Permanent Magnet Direct Current (PMDC) motor fed by DC boost converter is presented. The main idea of this work is to improve the energy efficiency of the conversion chain of an electric vehicle by inserting a boost converter between the battery and the four quadrant-DC motor chopper assembly. Consequently, this method makes it possible to maintain the amplification gain of the 4 quadrant chopper constant regardless of the battery voltage drop and even in the presence of a fault in the battery. One of the most important control problems is control under heavy uncertainty conditions. The higher order sliding mode control technique is introduced for the adjustment of DC bus voltage and mechanical motor speed. To implement the proposed approach in the automotive field, experimental tests were carried out. The performances obtained show the usefulness of this system for a better energy management of an electric vehicle and an ideal control under different operating conditions and constraints, mostly at nominal operation, in the presence of a load torque, when reversing the direction of rotation of the motor speed and even in case of battery chamber failure. The whole system has been tested experimentally and its performance has been analyzed.

• 한국진공학회지
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• 제16권2호
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• pp.153-159
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• 2007

KSTAR 장치의 저온 component에 헬륨을 공급하기 위한 헬륨라인은 크게 두 가지로 이루어져 있다. 냉동기에서 KSTAR 저온용기 외부까지의 트랜스퍼 라인과, 저온용기 내부의 헬륨라인이다. KSTAR 장치는 3가지 종류의 헬륨을 사용하여 각 저온 component를 냉각하는데, 초전도 자석 시스템과 버스라인에는 초임계 헬륨, 전류인입장치에는 액체 헬륨, 열차폐체에는 가스 헬륨을 공급한다. 저온용기 내부의 헬륨라인은 냉동기에서 저온용기 근처까지 연결된 배관을 저온용기 내부의 각 장치에 최단거리로 열손실 없이 설치하여 각 장치가 정상 작동하도록 하는데 그 목적이 있다. 저온용기 내부의 헬륨라인은 최대 20bar로 가압되는 운전시간 동안에 헬륨누설 없이 설치되어야 한다. 그리고 상온으로 부터의 복사열을 차단하기 위하여 다층절연제로 배관을 감싸주어야 하고 고전압 부분은 프리프레그 테잎으로 절연되어야 한다. 전기절연체는 세라믹과 스테인레스 스틸 튜브를 브레이징 접합 방법으로 연결하여 만들어진 것으론 배관과 배관, 배관과 저온 component간의 절연을 위해 사용되고, 헬륨라인과 동일하게 4.5K 초임계 헬륨온도에서 누설이 없어야 한다. 따라서 모든 전기절연체는 액체질소에 침전시켜 열충격을 가하고, 내부에 30 bar를 가압하여 진공 누설시험을 한다. 그리고 초전도 자석과 배관의 절연체로 사용되므로 15kV 고전압 절연 검사를 한다. 전기절연체의 세라믹 부분은 구조적 보강을 위하여 추가적으로 표면에 절연 작업을 한다. 현재 대부분의 저온용기 내부의 헬륨 라인은 설치 완료되어 있으며, 최종 검사가 진행 중이다.