• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.419-424
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• 1996

As track density increases, the effects of nonlinearity in pivot bearing of hard disk drive on the servo performance are becoming more important in considering the range of inertia force and the input torque during settling and tracking mode. Recently, an increasing attention is given to more precise experimental observations and modelings of pivot nonlinearity for achieving higher performance of servo control. In this paper, we propose a new model that shows an improved prediction of the pivot nonlinearity than existing preload-plus-two-slope model at matching simulations and experimental results in both time and frequency domains. Experimental measurements are carried out to validate and identify the specific nonlinearity presents in the pivot bearing when its in fine motion. Using the experimental results new model along with the existing one are characterized and compared for relevancies.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.10
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• pp.433-437
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• 2005

This paper studied Rotary type ultrasonic motor which has cross type stator. The stator consists of hollowed cross type metal which has four piezoelectric ceramics on the ends of cross bars. When two harmonic voltages which have 90$^{\circ}$ phase difference given to ceramics, the elliptical motion was generated in the inside tips. Inside tips are contact with rotor and these elliptical motions are rotate the rotor The finite element analysis was used to optimize the dimension and displacement of the stator. And the analyzed results were compared with the experimental results of the motor. As results, the speed and the torque of motor was increased by increasing width of the cross bar. And the speed and torque o( motor was not influenced to length of cross bar. The speed and torque was linearly increased by increasing voltage. The maximum torque was generated when the motor fabricated length of cross bar and width of ceramics in the ratio of 1:2.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.517-522
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• 2002

본 연구는 트랙터용 로타리날의 운동특성을 분석하는 연구로서, 로타리날의 운동특성 분석장치를 이용하여 기존에 국내에서 사용되는 로타리날로 경운 작업을 할 경우, 로타리날 운동 및 형상, 구조에 따른 운동특성을 정밀 분석하였다. 본 연구에서 분석된 문제점 및 보완점을 앞으로 개발될 에너지 절감형 트랙터 로타리날 개발에 필요한 주요 인자를 결정하기 위한 수단으로 사용하는 데 목적이 있으며, 그 구체적인 연구 결과는 다음과 같다. (1) 로타리날의 운동특성을 분석할 수 있는 로타리날 운동특성 분석 시스템을 설계, 제작하였다. (2) 분석 시스템 제어용 프로그램 Visual Basic 6.0 프로그래밍 언어를 사용하여 개발하였다. (3) 국내 로타리날 제조회사 4곳 및 외국 1개사 제품의 운동특성을 분석한 결과, B, C, E maker 제품이 로타리 경운 작업에 적합한 것으로 분석되었다. (4) B, C, E maker 제품에서 살펴보면, 토양을 절단할 때의 경심별 위치를 \circled3부분이 되도록 해야하며, 단면이 확실하게 닿지 않도록 단면의 경우 B maker 형상을 따라야 한다. 또한 배면이 토양에 닿는 부위가 적어야 한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.318-319
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• 2007

In this study, novel structured thin ultrasonic rotary motor has been proposed. Ultrasonic motors are based on an elliptical motion on the surface of elastic body. ATILA ver. 5.2.4 was used for optimizing stator. The motor was fabricated by using designed stator. And characteristics of the motor were compared with simulated results. When the motor was fabricated with these results, 935[rpm] speed was obtain by input voltage of 25[Vrms] at 93.5[khz].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.354-356
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• 2005

Novel structure ultrasonic motors which have cross type stator were designed and fabricated. Driving characteristics of the motors were analyzed and measured by changing the materials of the stator. This ultrasonic motor has stator with hollowed cross bar and the stator rotate the rotor using elliptical displacement of the inside tips. This motion is generated by lateral vibration mode of cross bars. This stator was analyzed by finite element analysis and the ultrasonic motors were made by analyzed results. The larger displacements were obtained, when the Young's modulus was increased and the Poisson's ratio was decreased. The fabricated one has high speed in large Poisson's ratio and Young's modulus. And the torque was increased in high Young's modulus.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.638-642
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• 2008

Computational methods based on the solution of the flow model are widely used for the analysis of lowspeed, inviscid, attached-flow problems. Most of such methods are based on the implementation of the internal Dirichlet boundary condition. In this paper, the time-domain panel method uses the piecewise constant source and doublet singularities. The present method utilizes the time-stepping loop to simulate the unsteady motion of the rotary wing blade. The wake geometry is calculated as part of the solution with no special treatment. To validate the results of aerodynamic characteristics, the typical blade was chosen such as, Caradonna-Tung blade and present results were compared with the experimental data and the other numerical results in the single blade condition and two blade condition. This isolated rotor blade model consisted of a two bladed rotor with untwisted, rectangular planform blade. Computed flow-field solutions were presented for various section of the blade in the hovering mode.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.507-514
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• 2001

Direct drive servovalve(DDV) is a kind of one-stage valve since the rotary motion of DC motor is directly transferred to the linear motion of valve spool through the link. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the classical controller is designed using the analytical Bode method.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1590-1595
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• 2003

Direct drive servovalve(DDV) is a kind of one-stage valve since the rotary motion of DC motor is directly transferred to the linear motion of valve spool through the link. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.754-763
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• 2002

Direct drive servovalve(DDV) is a kind of one-stage valve since the rotary motion of DC motor is directly transferred to the linear motion of valve spool through the link. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the classical controller is designed using the analytical Bode method.

• Smart Structures and Systems
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• v.33 no.3
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• pp.217-225
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• 2024

In this study, an electromagnetic dynamic vibration suppressor and energy harvester is designed and studied. In this system, a gear mechanism is used to convert the linear motion to continuous rotary motion. Governing equations of motion for the system are derived and validated using the experimental results. Effects of changing the main parameters of the presented system, such as mass ratio, stiffness ratio and gear ratio on the electro-mechanical behavior of system are investigated. Moreover, using so-called Weighted Cost Function, the optimum parameters of the system are obtained. Finally, it is shown that the presented electromagnetic dynamic vibration absorber not only can reduce the undesired vibration of the main system but also it can harvest acceptable electrical energy.