• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 춘계학술대회 논문집
• /
• pp.135-136
• /
• 2014

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2008년도 춘계학술대회 논문집
• /
• pp.313-314
• /
• 2008

• 대한기계학회논문집A
• /
• 제20권10호
• /
• pp.3079-3094
• /
• 1996

Recently, the high-precision vibration attenuation technology becomes the essence fo the seccessful development of high-integrated and ultra-precision industries, and is expected to continue playing a key role in the enhancement of manufacturing technology. Vibration isolation system using an air-spring is widely employed owing to its excellent isolation characteristics in a wide frequency range. It has, however, some drawbacks such as low-stiffness and low-damping features and can be easily excited by exogenous disturbances, and then vibration of table is remained for a long time. Consequently, the need for active vibration control for an air-spring vibration isolation system becomes inevitable. Furthermore, for an air-spring isolation table to be successfully employed in a variety of manufacturing sites, it should have a guaranteed robust performance not only to exogenous disturbances but also to uncertainties due to various equipments which might be put on the table. In this study, an active vibration suppression control system using H.inf. theory is designed and experiments are performed to verify its robust performance. An air-spring vibration isolation table with voice-coil-motors as its actuators is designed and built. The table is modeled as 3 degree-of-freedom system. An active control system is designed based on $H_\infty$control theory using frequency-shaped weighting functions. Analysis on its performance and frequency responce properties are done through numerical simulations. Robust characteristics of$H_\infty$ control on disturbances and model uncertainties are experimentally verified through (i) the transient response to the impact excitation of the table, (ii) the steady-state response to the harmonic excitation, and (iii) the response to the mass change of the table itself. An LQG controller is also designed and its performance is compared with the $H_\infty$ controller.

• 한국생산제조학회지
• /
• 제25권6호
• /
• pp.486-491
• /
• 2016

Disturbance/vibration reduction is critical in many applications using machine vision. The off-focusing or blurring error caused by vibration degrades the machine performance. In line with this, real-time disturbance estimation and avoidance are proposed in this study instead of going with a more familiar approach, such as the vibration absorber. The instantaneous motion caused by the disturbance is sensed by an attitude heading reference system module. A periodic vibration modeling is conducted to provide a better performance. The algorithm for vibration avoidance is described according to the vibration modeling. The vibration occurrence function is also proposed, and its parameters are determined using the genetic algorithm. The proposed algorithm is experimentally tested for its effectiveness in the vision inspection system.

• Earthquakes and Structures
• /
• 제13권1호
• /
• pp.51-58
• /
• 2017

Passive dynamic vibration absorbers (DVAs) are often used to suppress the excessive vibration of a large structure due to their simple construction and low maintenance cost compared to other vibration control techniques. A new type of passive DVA consists of two pendulums connected with spring and dashpot element is investigated. This research evaluated the performance of the DVA in reducing the vibration response of a two degree of freedom shear structure. A model for the two DOF vibration system with the absorber is developed. The nominal absorber parameters are calculated using a Genetic Algorithm(GA) procedure. A parametric study is performed to evaluate the effect of each absorber parameter on performance. The simulation results show that the optimum condition for the absorber frequencies and damping ratios is mainly affected by pendulum length, mass, and the damping coefficient of the pendulum's hinge joint. An experimental model validates the theoretical results. The simulation and experimental results show that the proposed technique is able be used as an effective alternative solution for reducing the vibration response of a multi degree of freedom vibration system.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.34-35
• /
• 2014

we designed a distributed mass dynamic vibration absorber for vibration reduction in a dual mode system. And we were subjected to evaluation of the vibration reduction performance of the distributed mass dynamic vibration absorber through experiments.

• Smart Structures and Systems
• /
• 제16권6호
• /
• pp.981-1002
• /
• 2015

For vibration control of civil structures, especially large civil structures, one of the important issues is how to place a minimal number of actuators and sensors at their respective optimal locations to achieve the predetermined control performance. In this paper, a methodology is presented for the determination of the minimal number and optimal location of actuators and sensors for vibration control of building structures under earthquake excitation. In the proposed methodology, the number and location of the actuators are first determined in terms of the sequence of performance index increments and the predetermined control performance. A multi-scale response reconstruction method is then extended to the controlled building structure for the determination of the minimal number and optimal placement of sensors with the objective that the reconstructed structural responses can be used as feedbacks for the vibration control while the predetermined control performance can be maintained. The feasibility and accuracy of the proposed methodology are finally investigated numerically through a 20-story shear building structure under the El-Centro ground excitation and the Kobe ground excitation. The numerical results show that with the limited number of sensors and actuators at their optimal locations, the predetermined control performance of the building structure can be achieved.

• 한국항공우주학회지
• /
• 제35권6호
• /
• pp.533-538
• /
• 2007

위성 탑재체의 지향성능을 향상시키기 위하여 반수동 진동제어법을 제안하고, 시뮬레이션에 의해 진동절연 효과를 검증하였다. 본 논문에서 제안한 반수동 진동제어법은 고주파수 영역에서의 저댐핑 수동제어와, 구조물의 공진을 포함하는 저주파수 영역에서의 고댐핑 수동제어가 갖는 진동절연 효과를 동시에 만족시키기 위해 고안되었다. 시뮬레이션 결과는 반수동 진동제어법이 상기의 효과를 구현하는데 있어 효과적임을 나타낸다.

• 한국소음진동공학회논문집
• /
• 제25권5호
• /
• pp.313-320
• /
• 2015

A 2-axis gimbal-type X-band antenna has been widely used to effectively transmit the high resolution image data from the observation satellite to the desired ground station. However, a discontinuous stepper motor activation for rotating the pointing mechanism in azimuth and elevation directions induces undesirable micro-vibration disturbances which can result in the image quality degradation of a high-resolution observation satellite. To enhance the image quality of the observation satellite, attenuating the micro-vibration induced by an activation of the stepper motor for rotational movements of the antenna is important task. In this study, we proposed a low-rotational-stiffness blade gear applied to the output shaft of the stepper motor to obtain the micro-vibration isolation performance. The design of the blade gear was performed through the structure analysis such that this gear is satisfied with the margin of safety rule under the derived torque budget. In addition, the micro-vibration isolation performance of the blade gear was verified through the micro-vibration measurement test using the dedicated micro-vibration measurement device proposed in this study.

• 비파괴검사학회지
• /
• 제31권2호
• /
• pp.111-117
• /
• 2011

Vibration monitoring is required for reliable thermosonic testing to decide whether sufficient vibration is achieved in each test for the detection of cracks. From a practical point of view, a cheaper and convenient monitoring method is better for the application to real tests. Therefore, the performance of different sensors for vibration monitoring was investigated and compared in this study to find a convenient and acceptable measurement method for thermosonics. Velocity measured by a laser vibrometer and strain provide an equivalent HI when measured at the same position. The microphone can provide a cheaper vibration monitoring device than the laser and the heating index calculated by a microphone signal shows similar characteristics to that calculated from velocity measured by the laser vibrometer. The microphone frequency response shows that it underestimates high frequency components but it is applicable to practical tests because it gives a conservative value of HI.