• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.618-622
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• 2004

The vibration test system of SITC(Satellite Integration and Test Center) at KARI(Korea Aerospace Research Institute) has been used successfully for the environmental tests of a majority of korean space programs, such as KOMPSAT, Koreasat KITSAT, STSAT and KSR program since 1996. To meet the recent needs of large size test facility available for the vibrational tests of the huge launch vehicles and tole-communication satellites which will be developed in the near future, KARI undertook to construct the large size multi-electromagnetic shaking system with 3 $\times$ 3m head expander system. The new system will consist of three electromagnetic shakers which has 160 kN thrust force individually, and be able te sustain up to 8 tons test load and 300 kNm overturing moment. And to avoid the tremendous cost and effort to furnish the seismic block with large size and weight, it will adopt a Lin-E-Air type configuration with which the seismic block is less severe than a Solid-Truninon type. In addition, to fulfill the strong requirement of high overturning moment the additional guidance system including a central bearing system on a central support and several pad bearings around the head expander body is now considered. This paper describes the configuration and the design parameters of the multi-shaking system which is under development by KARI's engineers.

• Explosives and Blasting
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• v.35 no.1
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• pp.43-52
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• 2017

Mountain and hill areas occupy by more than 70% in South Korea and Rock drilling should be applied in order to reduce noisy & vibration from massive civil engineering business such as road expansion, high-way construction, subway construction and construction of site renovation such as a newly-built & re-development of apartment, newly-built of high-rising building in downtown area. As Blasting noise & vibration such as vibration, noise, fly rock etc caused by blasting operation from large small scale construction occurs, neighboring residents who demand the compensation file a civil complaint so that the business reach a deadlock. As the excavation method for these areas, There are blasting of micro-vibration, mechanical excavation method(Rock splitter, Breaker etc), similar blasting method(plasma, gel fragmentation etc) to date. In this study, we are trying to find the feature & performance which get improved economic feasibility & construct ability through improving sympathetic detonation of New KINECKER-I used in blasting of micro-vibration & formulation and would provide convenience for use by introducing standard blasting pattern & construction method. Also, checked and confirmed all the blasting with connecting cap has been cleary detonated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.7
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• pp.1127-1140
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• 1997

With the study for identifying the transmission characteristics of vibration and noise generated by operating engine system of a vehicle, recently many engineers have studied actively the reduction of vibration and noise inducing uncomfortableness to the passenger. In this study, output noise was analyzed by multi-dimensional spectral analysis and vector synthesis method. The multi-dimensional analysis method is very effective in case of identification of primary source, but this method has little effect on suggestion for interior noised reduction. For compensation of this, vector synthesis method was used to obtain effective method for interior noise reduction, after identifying primary source for output noise. In this paper, partial coherence function of each input was calculated to know which input was most coherent to output noise, then with simulation of changes for input magnitude and phase by vector synthesis diagram, the trends of synthesized output vector was obtained. As a result, the change of synthesized output vector could be estimated.

• Journal of Korea Multimedia Society
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• v.23 no.8
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• pp.1040-1048
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• 2020

In this study, in order to improve the implantable bone conduction transducer of the prototype proposed by Shin et al., the effect of the element parameters of the transducer on the frequency characteristics was analyzed using electromagnetic and mechanical vibration analysis. Electromagnetic analysis was performed on the size of the permanent magnet and the distance between the metal plate and the coil to derive an optimal structure that generates the maximum Lorentz force. In addition, mechanical vibration analysis was performed on the cantilever structure of the vibrational membrane in order to minimize the distortion of the transducer and to have a frequency characteristic suitable for conductive hearing loss compensation. The frequency characteristics of the transducer of the optimal structure derived through finite element method were compared with the simulation results of the previous transducer. As a result, the output magnitude (displacement) of the transducer designed with the optimal structure generated an average 8.8 times higher than the previous transducer, and the resonance frequency was generated at 0.9 kHz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.157-162
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• 1990

기계의 정밀도 향상을 위하여는 기계에 대한 보다 정확한 해석을 요구한다. 그러나 실제 기계 시스템은 마찰, Backlash, Saturation등과 같은 비서형 특 성을 가지고 있어 시스템의 해석 및 제어가 어렵게 된다. 특히, 축, 링크, 기 어, 풀리, 베어링등의 기계요소에서는 마찰로 인해 정밀도가 크게 덜어지고 있어, 마찰에 의한 동특성 및 제어는 많은 연구자들에 의해 관심의 대상이 되어 왔다. 마찰력을 고려한 기계시스템의 운동은 정지상태 근처에서 마찰력 의 변화가 심한 비선형 동특성을 보이고 있어 그 해석에 어려움을 겪고 있 다. 실제 마찰이 저속에서 고급 비선형임에도 불구하고 가장 널리 사용되는 형태의 모델로서 쿨통 마찰을 고려한 운동방정식 조차 비선형성으로 인하여 해석에 어려움이 따르고 있다. 마찰은 오랜동안 연구되어 오면서 Fig.1, Fig2 와 같이 등가선형점성 감쇠, 쿨통마찰, 정적마찰로 모델화되거나 이들의 조 합으로 나타내었다[1-5]. 마찰력은 시간영역에서도 연구되어 Walrath[7]는 Fig.3-a의 속도가 역전되는 지점에서 마찰토오크가 .+-.Tf를 공유하는 문제 를 고려하기 위해, Fig.3-b와 같이 동적마찰모델을 사용하였다. 최근의 연구 로서 Armstrong[7]은 마찰의 위치의존성을 고려한 정확한 마찰모델을 설정 하여 개루프제어에 적용, 좋은 제어특성을 확인하였고, Canudas[8]는 저속영 역에서 overcompensation시 limit cycle과 gain의 관계를 해석하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.4
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• pp.361-372
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• 2010

Optical image stabilization is a technique to compensate the image blurring caused by some vibrations of camera at the exposure time. Pitching and yawing of camera are sensitive to the image quality so they are usually compensated by optical image stabilization. Corresponding pitching and yawing of a camera, a lens or the image sensor is translated in two-axis direction and then the optical path of camera is adjusted. In this paper, two-axis OIS actuator for mobile camera module is suggested and designed. The actuator is a voice-coil actuator that uses the electromagnetic force of voice-coil to make compensation motions. And ball bearing is used to reduce friction force. Magnetic attractive force between magnets and yokes acts as a preload and magnet springs. Prototype actuator is fabricated to measure the friction force and to verify the feasibility of the OIS actuator with ball bearing. At last, the actuator is improved in consideration of driving force and friction force. Design of experiments is used for designing the actuator.

• Transactions of the Society of Information Storage Systems
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• v.7 no.2
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• pp.70-74
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• 2011

The mobile camera module is a device to be inserted in the digital device for camera feature. The mobile camera module is being shaken by vibrations such as handshake during the exposure time. The clarity is compromised by these vibrations, thus the vibration is considered as an external disturbance. Moreover the use of mobile camera module has been being expanded for automotive vibration should be considered. These external disturbances can cause image blurring, thus optical image stabilization should be applied for image compensation. The compensator is fulfilled mechanically by movable lens group or image sensor that adjusts the optical path to the camera movement. Open loop control is useful for well-defined systems like compliant mechanism. Notch filter and lead compensator are designed and applied to improve the stability and bandwidth. The final level of image compensating is confirmed by image processing with MATLAB and CODE V to verify the better performance.

• Journal of Aerospace System Engineering
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• v.9 no.4
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• pp.23-30
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• 2015

The focal plane image stabilization for a camera is one of the most effective method that can increases the digital camera's image quality by compensating the vibration disturbance. The optical image stabilization can be implemented by making the focal plane to trace the path of incident light. To control the position of focal plane motion compensating stage precisely, a nonlinear control algorithm has been applied by considering coulomb friction which is nonlinear behavior of the compensator system. In our study, we have analyzed the hand shaking vibration using the gyro sensor, and made a mathematical model of compensating stage containing optical sensor and piezo-actuator. Then the nonlinear control algorithm has been designed and its performance has been verified by experiment. In this study, a friction driven peizo-electric actuator with $1{\mu}m$ resolution and 10mm/s speed has been used for stage movement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.754-758
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• 2000

In recent years, the LDM(Linear DC Motor) is widely used, because it has more merits than other rotary motors. First, if system requires linear motion, LDM realizes direct linear motion as rotary motor does not. Second, system is simple and easy to control, and so on. In optical disc drive, a tracking system consists of two parts. One is fine actuating and the other is coarse actuating. For coarse actuating VCM(Voice Coil Motor) actuator is used as a basic drive mechanism. In this paper, MC(Moving Coil) type LDM is designed, manufactured and controlled. System is composed of mechanical-electromagnetic component, therefore mechanical loss and electromagnetic loss exist. The dominent mechanical loss is friction which results from sliding between guide shaft and hole. Therefore, this paper shows the friction compensation control. High speed and accurate position is not gained only PID control, therefore other control method is applied to the system.

• Journal of Computational Design and Engineering
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• v.2 no.4
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• pp.206-217
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• 2015

This paper presents a complete S-shape feed rate scheduling approach (CSFA) with confined jerk, acceleration and command feed rate for parametric tool path. For a Non-Uniform Rational B-Spline (NURBS) tool path, the critical points of the tool path where the radius of curvature reaches extreme values are found firstly. Then, the NURBS curve is split into several NURBS sub-curves or blocks by the critical points. A bidirectional scanning strategy with the limitations of chord error, normal/tangential acceleration/jerk and command feed rate is employed to make the feed rate at the junctions between different NURBS blocks continuous. To improve the efficiency of the feed rate scheduling, the NURBS block is classified into three types: short block, medium block and long block. The feed rate profile corresponding to each NURBS block is generated according to the start/end feed rates and the arc length of the block and the limitations of tangential acceleration/jerk. In addition, two compensation strategies are proposed to make the feed rate more continuous and the arc increment more precise. Once the feed rate profile is determined, a second-order Taylor's expansion interpolation method is applied to generate the position commands. Finally, experiments with two free-form NURBS curves are conducted to verify the applicability and accuracy of the proposed method.