• Proceedings of the KSR Conference
• /
• 2007.05a
• /
• pp.477-485
• /
• 2007

When Korean High Speed Train (KTX) runs over a high-speed railway bridge, the high-speed railway bridge gives quite large acceleration response. Local vibration at the large cross section, the impact from equally spaced sleepers, the vibration due to elastomeric bearings, and the vibration from the train itself are the causes of this acceleration response. Maximum peaks of the accelerations measured at the bridges are sometimes going over the limit value. Although it is smaller than 0.35G, the limit from the Korean Bridge Design Manual(BRDM), this acceleration response should be reduced for the safety of running trains with high speed. In this paper, to reduce the acceleration response by controlling excessive local vibration at the large cross section, vibration reduction method is studied. The result shows that the effect of elastomeric bearings on the vibration of the bridge is very large and that the vibration reduction device is effective against wing mode local vibration PSC box girder bridge for the high-speed railway, which usually has very large cross section, although it has little effect on global vibration modes such as flexural and twisting modes. The test of the vibration reduction device on the bridge in service has been performed in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.11a
• /
• pp.282-286
• /
• 2000

In this paper, magneto-rheological(MR) damper is studied for vibration control of large infra structures under earthquake. Generally, active control devices need a large control force and a high power supply system to reduce the vibration effectively. Large and miss tuned control force may induce the dangerous situation such that the generated large control force acts to amplify the structural vibration. Recently, to overcome the weaknesses of the active control, the semi-active control method is suggested by many researchers. Semi-active control uses the passive control device of which the characteristics can be modified. Control force of the semi-active device is not generated from the actuator with power supply. It is generated as a dynamic reaction force of the device same as in the passive control case, so the control system is inherently stable and robust. Unlike the case of passive control, control force of semi-active control is adjusted depending on the measured response of the structure, so the vibration can be reduced more effectively against various unknown environmental loads. Magneto-rheological(MR) damper is one of the semi-active devices. Dynamic characteristics of the MR material can be changed by applying the magnetic fields. So the control of MR damper needs only small power. Response time of MR to the input voltage is very short, so the high performance control is possible. MR damper has a high force capacity so it is adequate to the vibration control of large infra structure. Because MR damper has a nonlinear property, normal control method used in active control may not be effective. Clipped optimal control, modified bang-bang control etc. have been suggested to MR damper by many researchers. In this study, sliding mode fuzzy control(SMFC) is applied to MR damper. Genetic algorithm is used for the controller tuning. To verify the applicability of MR damper and suggested algorithm, numerical simulation on the aseismic control is carried out. Simulation model is three-story building structure, which was used in the paper of Dyke, et al. The control performance is compared with clipped optimal control. The present results indicate that the SMFC algorithm can reduce the earthquake-induced vibration very effectively.

• Journal of Space Technology and Applications
• /
• v.2 no.3
• /
• pp.187-194
• /
• 2022

Although the magnitude of the disturbance caused by the driving of the motor operated to secure the high-speed and precise directivity of the antenna is small, it acts as a major cause of impairing the image quality of the observation satellite, which requires precision directing performance. In order to acquire high-resolution image information through the improvement of the high-resolution observation satellite, proper vibration isolation and reduction design are required so that jitter generated when the directional antenna motor is driven is not transmitted to the main mission equipment. In this paper, the development process of the directional antenna vibration reduction device applied to real satellites and the effect of micro vibration reduction before and after application will be examined. This device was designed as a way to significantly improve the jitter problem by replacing only one gear in the directional antenna driving unit with a spring damper gear without any additional interface equipment. It was first applied and launched to a high-resolution earth observation satellite, and has been successfully operated so far.

• Design & Manufacturing
• /
• v.14 no.4
• /
• pp.25-39
• /
• 2020

In this study, an edge device that monitors the injection molding process by measuring the mold vibration(acceleration) signal and the mold surface temperature was developed and evaluated its performance. During injection molding, signals of the injection start, V/P switchover, and packing end sections were obtained through the measurement of the mold vibration and the injection time and packing time were calculated by using the difference between the times of the sections. Then, the mold closed and mold open signals were obtained using a magnetic hall sensor, and cycle time was calculated by using the time difference between the mold closed time each process. As a result of evaluating the performance by comparing the process data monitored by the edge device with the shot data recorded on the injection molding machine, the cycle time, injection time, and packing time showed very small error of 0.70±0.38%, 1.40±1.17%, and 0.69±0.82%, respectively, and the values close to the actual were monitored and the accuracy and reliability of the edge device were confirmed. In addition, it was confirmed that the mold surface temperature measured by the edge device was similar to the actual mold surface temperature.

• Earthquakes and Structures
• /
• v.6 no.3
• /
• pp.281-300
• /
• 2014

This study proposes a scheme to design control parameters for a data center facility with a vibration controller on its top floor and a secondary isolation device with its own vibration controller designed to protect vibration-sensitive computer equipment. The aim is to reduce the effects of acceleration and drift from an earthquake on computer servers placed on the isolation device that must operate during a seismic event. A linear elastic model is constructed and the evaluation function of the linear quadratic Gaussian (LQG) control is formulated. The relationship between the control parameters and the responses is examined, and based on the observations, a control parameter design scheme is constructed to reduce the responses of both the building and the computer server effectively.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.9
• /
• pp.78-85
• /
• 2008

Piezoelectric materials have been investigated as vibration energy converters to power wireless devices or MEMS devices due to the recent low power requirements of such devices and the advancement in miniaturization technology. Piezoelectric power generation can be an alternative to the traditional power source-battery because of the presence of facile vibration sources in our environment and the potential elimination of the maintenance required for large volume batteries. This paper represents the new power source which supplies energy device node. This system, called "energy harvesting system", with piezo materials scavenges extra energy such as vibration and acceleration from the environment. Then it converts the mechanical energy scavenged to electrical energy for powering device This paper explains the properties of piezo material through theoretical analysis and experiments The developed system provides a solution to overcome the critical problem of making up wireless device networks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.571-576
• /
• 2006

A Color Discerning Device(CDD) is the equipment to use in Rice Processing Complex(RPC). By use a high-speed charge-coupled device camera, CDD can sorting discolored grain according to light and shade. The existing CDD's driving performance is not so good as overseas machine. Besides, transportation process causes a defect in the mechanism from impact or harmonic excitation or etc. This study is represented the problem of CDD through modal analysis and static analysis by using ANSYS workbench. To analysis the problem of driving condition, devide each part of CDD for performed modal analysis. The problem of driving condition and transportation process solved by carry out modal analysis and static analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.422-427
• /
• 2006

This paper presents force-feedback control performance of a haptic device in virtual environment of minimally invasive surgery(MIS). As a first step, based on an electrorheological(ER) fluid and spherical geometry, a new type of master device is developed and integrated with a virtual environment of MIS such as a surgical tool and human organ. The virtual object is then mathematically formulated by adopting the shape retaining chain linked(S-Chain) model. After evaluating reflection force, computational time, and compatibility with real time control, the virtual environment of MIS is formulated by interactivity with the ER haptic device in real space. Tracking control performances for virtual force trajectory are presented in time domain, and theirtrackingerrorsareevaluated.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.12 s.117
• /
• pp.1286-1293
• /
• 2006

This paper presents force-feedback control performance of a haptic device in virtual environment of minimally invasive surgery(MIS). As a first step, based on an electrorheological (ER) fluid and spherical geometry, a new type of master device is developed and integrated with a virtual environment of MIS such as a surgical tool and human organ. The virtual object is then mathematically formulated by adopting the shape retaining chain linked(S-chain) model. After evaluating reflection force, computational time, and compatibility with real time control, the virtual environment of MIS is formulated by interactivity with the ER haptic device in real space. Tracking control performances for virtual force trajectory are presented in time domain.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.21 no.3
• /
• pp.206-211
• /
• 2011

In this paper, we report a high-precision wireless gap sensor based on a surface acoustic wave (SAW) device. The sensing element is a parallel-plate capacitor whose dimensions are $3{\times}3\;mm^2$, and is attached to the SAW device as an external load. The SAW device, equipped with an RF antenna, serves simultaneously as a signal conditioner and an RF transponder. The center frequency of the SAW device is 450 MHz. The wireless gap sensor prototype exhibits a resolution of 100 nm and a sensing range of $50{\mu}m$. The proposed sensor system can be used for remote, high-precision gap measurement in hard-to-reach environments.