• Journal of Korean Orthopaedic Sports Medicine
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• v.7 no.2
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• pp.128-134
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• 2008

Purpose: We prospectively evaluated the clinical usefulness of the patellar inferior pole (PIP) as a landmark of the anteromedial (AM) portal for the arthroscopic surgery of the medial mensiscus posterior horn (MMPH). Materials and Methods: Group 1 (50 normal left knees of adults), Group 2 (10 normal knees under anesthesia), and Group 3 (50 consecutive knees undergoing elective arthroscopic surgery for relatively simple intraarticular pathologies, or diagnostic arthroscopy) were included. In Group 1 and 2, the true lateral (A) and valgus stress lateral radiographs (B) on $30^{\circ}$ flexion were obtained, and the lines (AM portal line) passing through the PIP and distal-most medial femoral condyle (MFC) were drawn under the condition without considering the thickness of articular cartilage of MFC (1, 2-A, B group), and considering it as 2.5mm on B (1, 2-C group). Then, we investigated the meeting point of the AM portal line with medial tibial plateau (C-D percentage), and measured the distance between the PIP and the anterior joint line (E-length), and medial tibial-femoral joint space (F-length). In Group 3, the AM portal was made at the PIP level and clinical usefulness of the approach to the MMPH and body of the lateral meniscus (LM) was analyzed. Results: The average C-D percentage came out as 85.8, 101.3, 69.1% for each Group 1-A, B, C, and 102.4, 144.6, 116.8% for each Group 2-A, B, C. Measured E-length was an average of 15.1 (Group 1-A), 15.5 (Group 1-B, C), 13.1 (Group 2-A), and 12.9 mm (Group 2-B, C) and the change by valgus stress had no statistical significance. The F-length increased about 1.2 (Group 1) and 3.6 mm (Group 2) when valgus stress was applied, which had statistical significance (p<0.001, p<0.001). In Group 3, 49, 48 knees were classified as good for the MMPH, and the body of LM in aspect of the clinical usefulness of AM portal made on the PIP level. Conclusion: We identified the clinical usefulness of the PIP as a skin landmark of AM portal for the arthroscopic surgery of the MMPH.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.4
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• pp.193-199
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• 2001

This paper suggests a novel single-stage drive for a switched reluctance motor (SRM) to achieve sinusoidal, near unity power factor input currents. The proposed drive is very simple without additional active switch. As a single-stage approach, which combines a DC link capacitor used as dc source and a drive used for driving the motor into one power stage, a simple structure and low cost drive in implemented. A prototype drive for an 8/6 pole SRM equipping a suitable encoder is designed to evaluate the proposed topology. Also subscription control algorithm is presented. The characteristics and validity of the proposed circuit will be discussed in depth through the experimental results.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.97-98
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• 2016

일반적으로 산업체에서 사용되는 전압형 PWM(Pulse Width Modulation) 인버터는 2개의 스위칭 소자가 직렬 연결된 단상하프 브릿지 회로를 기본 회로로 사용한다. 보통 극(pole), 암(arm) 또는 레그(leg)라 불리며 상보적으로 스위칭한다. 하지만 게이팅 신호 전달의 시지연과 스위치의 온-오프 시간차이에 의해 두 스위치가 동시에 켜지는 단락 사고를 방지하기 위해 데드 타임을 사용한다. 데드 타임은 직렬 연결된 두 스위치를 동시에 끔으로써 인버터의 안정적인 동작을 보장하지만 인버터 출력 전압 제어가 불가능하여 전압 및 전류 왜곡과 소음, 진동을 야기한다. 본 논문에서는 데드 타임 보상을 위한 적절한 전압 선정 방법에 대해 알아본다. 데드 타임 보상 전압 선정을 위해 부하 전류의 6고조파 성분을 추출, 비교하여 적절한 데드 타임 보상 전압을 선정하였으며 실험을 통해 그 유효성을 검증하였다.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.119-122
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• 2002

The NiO buffer layers for YBCO coated conductor were prepared on textured Ni substrates by MOCVD method and the degree of texturizing and the surface roughness were analyzed X-ray pole figure and AFM and SEM. Processing variables were oxygen partial pressure and substrate temperature. (200) textured NiO layer was formed at 450~$470^{\circ}C$ and oxygen partial pressure of 1.67 Torr. Out-of-plane($\omega$-scan) and in-plane($\Phi$-scan) texture were $10.34^{\circ}$ and $10.00^{\circ}$ respectively. The surface roughness estimated by atomic force microscopy was in the range of 3.1~4.6 nm.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.6
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• pp.299-305
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• 2006

In this paper, we suggest a new space vector PWM modulation method with very short processing time which does not need identification of nearest three vectors(NTV) and duty ratio for each vector. The suggested PWM method makes mean value of phase voltage to be same as reference during every modulation period by use of a triangle in small hexagon on multi-level vector space. This paper described the suggested modulation method can be successfully applied to the space vector modulation use of multi-level inverter by computer simulations and experiments.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.6-8
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• 1996

Induction Motors are preferred because of their ability to achieve higher power density, efficiency and reliability than permanent DC Motors for Electric Vehicle Drives. This paper describes induction motor design procedure to achieve high power density for EV using nonlinear optimization technique. Objective functions are considered to improve power density and a set of eight design variables is identified. As a numerical example, an induction motor of 15kW, 3 phase and 4 pole is designed.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.327-332
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• 1993

One maglev vehicle is composed of 6 r 8 modules. Each module is composed of 4 staggered magnets attached to an aluminum bogie. In the view point of levitation control except propulsion by LIM, 5 is the maximum degrees of freedo to be controlled. But rolling control of the vehicle depends on the bogie structure. We describe just anti-roll type out of bogie structures and 4 degrees of freedom control is sufficient for levitation quality improvement. Multivariable pole-placement concept and the decentralized control concept are used for controller design. Computer simulation and control experiment are performed on a specially designed test module.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.111-114
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• 2005

The isolation performance of the S-band single-pole single-throw (SPST) monolithic microwave integrated circuit (MMIC) switch with two different RF-interconnection approaches, microstrip and grounded coplanar waveguide (GCPW) lines, are investigated. On-to-off isolation is improved by 5.8 dB with the GCPW design compared with the microstrip design and additional improvement of 6.9dB is obtained with the coplanar wire-bond interconnection (CWBI) at 3.4 GHz. The measured insertion loss and third-order inter-modulation distortion (IMD3) are less than 2.43 dB over 2.5 CHz $\sim$ 4 GHz and greater than 64 dBc.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.235-243
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• 1998

For motor operation at low speeds and loads, torque pulsation by the cogging torque is often a source of vibration and control difficulty. In this paper, the magnetic field of a motor is calculated by finite element method. The periodic cogging torque is determined using Maxwell stress method and time stepping method, and then decomposed using fourier series expansion, The purpose of this paper is to characterize design parameters on the cogging torque and to design a permanent magnet motor with a cogging torque less vulnerable to vibration, without sacrificing the motor performance. The design parameters include stator slot width, permanent magnet slot width, airgap length and magnetization direction. A new design with a less populated frequency spectrum of the cogging torque is proposed after characterizing individual effect of design parameters. Magnet pole edge shaping, by gradually increasing the cogging torque with reduced higher harmonics.

• Journal of KSNVE
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• v.6 no.3
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• pp.357-362
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• 1996

The magnetic levitation system has great advantages, such as little friction, no lubrication, no noise and so on. But the magnetic levitation system need a stabilizing controller because it is a unstable, system in natural and it need a sensor for displacement measurement to control the system. In this paper, we proposed a sensorless method to measure the gap between the magnetic pole and the levitated object with application the inductance characteristic which vary according to gap. We made a driving circuit which supply simultaneously the control input PWM(Pulse Width Modulation) signal and the carrier PWM signal to estimate the gap. Because the inductance is a function of gap, and the current of the carrier signal is a function of the inductance, we could estimate the gap from the measurement of the current of the carrier signal. Finally, we investigated the validity of the proposed method through the experimental results.