• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.295-299
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• 2004

본 논문에서는 주기 비안정 연속계의 해석을 위한 주파수 방법이 제안된다. 비안정시스템의 안정화를 위한 기존의 주파수 해석법을 일부 수정하여 연속계를 포함한 비안정 시스템에 적합하도록 수정하였으며, 직류모터와 동기발전기로 구성되어 있는 전기-기계 시스템에 적용하여 유용성을 보였다. 복잡한 비안정 연속계의 문제를 각 요소별 주파수 응답을 분리하고 조합하는 작업들을 통하여 쉽게 풀 수 있음을 보였다. 모터-발전기로 구성되어있는 전기-기계 시스템에서 발전기의 상호유도인덕턴스의 시간에 따른 주기적 변화와 장선(long electrical line)의 부하가 시스템의 불안정성을 야기함을 보였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.217-224
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• 2000

This paper proposes a new type of HDD suspension integrated with shape memory alloy(SMA) actuator in order to prevent the friction between the slider and the disk. A finite element analysis is undertaken to investigate modal characteristics of the proposed self loading/unloading slider. The dynamic model is formulated and its validity is proved by comparing the predicted displacement transmissibility with the measured one. A control model is then established by integrating experimentally-obtained SMA actuator dynamics. Subsequently, a sliding mode controller is designed to achieve non-contact start/stop(Non CSS) modes, and control results are presented in time domain.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.237-242
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• 2000

The areal recording density of HDD(Hard Disk Drive) has been increasing by about 60% a year. In order to achieve high areal density, less track pitch is expected and more servo bandwidth is required. Dual stage actuator and servo controller for HDD have been suggested for achieving high track density as a possible solution. Dual-loop servo system is generally classified into a two-input-two-output system, but if we use an estimator for a two-input-two-output system, it can be converted into two input one output system. Since we can't control the dual stage servo system by the classical method, it requires a special technique; for example, Parallel Loop System, Master-Slave Loop System, Decoupled Master-Slave Loop System, and Dual Feedback Loop System. In this paper, we performed experimental evaluations of several types of control algorithm. Further experiments will be made in the future.

• Journal of Preventive Medicine and Public Health
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• v.28 no.4 s.51
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• pp.765-771
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• 1995

This study was performed to investigate the possibility of temporary threshold shift (TTS) of vibration sense could induced by exposure to high-frequency vibration or by work position taking by dentists in drilling or polishing. The vibratory perception thresholds (VPT) of 28 healthy men were measured on the index fingertip pulp of dominant hand at 250 Hz. The vibrating tool used in test was a low-speed handpiece of 34,000 rpm. For the TTS test, the dominant hand was exposed to high-frequency vibration and to work position for five minutes, respectively. The VPTs before and after vibratory exposure were $23.5{\pm}3.5dB,\;30.8{\pm}4.2dB$, respectively and VPT after work position was $23.7{\pm}4.6dB$. The difference between before and after vibartory exposure was statistically significant (p<0.001). The correlation of height, weight and BMI with baseline VPTs was not statistically significant. Also, there was no difference of VPTs by smoking. These results suggest that high-frequency vibration from dental handpieces might cause the impairment of vibration sensation.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.6-8
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• 2003

Electromagnetic system of motor is being minimized by superior magnetic material and advanced design technology. But this type of motor causes a serious vibration. This is a big problem of motor operation. To decrease a vibration, motor is need to be designed considering mechanical vibration. This paper study about torque, natural frequency and mechanical vibration according to displacement.

• 대한예방의학회:학술대회논문집
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• 1993.10a
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• pp.115-116
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• 1993

• Proceedings of the Acoustical Society of Korea Conference
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• 1997.06a
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• pp.5-8
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• 1997

음성신호는 성대를 통과한 공기 흐름의 성질에 따라 유성음과 무성음으로 구분될 수 있다. 그 중 유성음에서는 성대의 규칙적인 지동이 존재하게 된는 데 이때 성대가 닫히는 순간을 GCI(Glotal Closure Instant)라 하며 성대 진동의 기본주기를 피치라고 한다. 이러한 피치는 음성합성, 음성인식, 피치동기 음성신호의 분석등에 중요한 파라미터 중의 하나이다. 본 논문에서는 가우시안 함수의 일차미분형태를 갖는 웨이브렛 함수를 사용할 경우 신호의 급격한 변화부분을 검출할 수 있다는 성질을 이용하여 음성 신호의 GCI를 찾아내고 이를 이용하여 피치를 검출하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.85-92
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• 2007

This paper presents a design optimization of a new Advanced Active Blade Twist (AATR-II) blade incorporating single crystal Macro Fiber Composites (MFC) and conducts vibratory loads reduction analysis using an obtained optimal blade configuration. Due to the high actuation performance of the single crystal MFC, the AATR blade may reduce the helicopter vibration more efficiently even with a lower input-voltage as compared with the previous ATR blades. The design optimization provides the optimal cross-sectional configuration to maximize the tip twist actuation when a certain input-voltage is given. In order to maintain the properties of the original ATR blade, various constraints and bounds are considered for the design variables selected. After the design optimization is completed successfully, vibratory load reduction analysis of the optimized AATR-II blade in forward flight condition is conducted. The numerical result shows that the hub vibratory loads are reduced significantly although 20% input-voltage of the original ATR blade is used.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.408-415
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• 2011

Advanced tanks in the future combat system are expected to have the trends of large caliber, high explosive shell and light weight for destructive power and improvement in mobility. Their guns are required to have longer barrels to meet increased muzzle exit velocities. However, as the length of the barrel is extended, the vibrations induced by the breech forces in fire and the terrain lead to increased muzzle pointing errors. Therefore, the fire-induced and terrain-induced vibrations must be attenuated. A method to reduce these vibrations without the significant increase of the gun mass is to use the forward thermal shroud as part of a tuned mass damper. In this study, the dynamically-tuned-shroud using this shroud and leaf springs is introduced and its effectiveness on the vibration attenuations of the barrel are verified. The parametric studies on the stiffness of these leaf springs are performed and the analytical results are verified using the experimental model of the dynamically-tuned-shroud.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.2
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• pp.285-290
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• 2013

The slotless linear synchronous motor(LSM) has the advantages that the structure of the mover is simple and it can control the trust force ripple by make the magnetic energy in a gap uniform by removing a slot of the primary iron core. Also, the application of the transportation system is becoming expansion because it high efficiency drive is possible and compares with the other LSM as control is more excellent. However, the application of the living field was unsatisfactory. Therefore, in this study, we examined the drive characteristics by the position feedback control for the living field application of the slotless LSM and we prove useful of the controller through load loading and the acceleration changing to get minimization of the speed vibration and stable answer characteristics.