• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.88-94
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• 2007

A flexure hinge-based compliant stage driven by stack-type piezoelectric elements has high precision motion but small operational range due to the characteristics of the piezoelectric element. Since the common flexure hinges can be broken by excessive deflection when the displacement is amplified by a high amplification ratio, a flexure hinge mechanism for large deflection is required. A cartwheel-type flexure hinge has an advantage of larger deflection compared with the common flexure hinges. This study presents a rotation stage with cartwheel-type flexure hinges driven by a stack-type piezoelectric element. The characteristics and the performance of the rotation stage are described by the terms of principal resonance frequency, amplification ratio of rotational displacement, maximum rotational displacement and block moment, in which the terms are analyzed by geometric parameters of the rotation stage. The analyzed results will be used as the guideline of the design of the rotation stage.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.70-74
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• 2007

This paper describes the development of a nano-positioning system for nanoscale science and engineering. Conventional positioning systems, which can be expensive and complicated, require the use of laser interferometers or capacitive transducers to measure nanoscale displacements of the stage. In this study, a new self-displacement sensing (SDS) nano-stage was developed using mechanical magnification of its displacement signal. The SDS nano-stage measured the displacement of its movement using a position-sensitive photodiode (PSPD), a laser source, and a hinge-connected rotating mirror plate. A beam from a laser diode was focused onto the middle of the plate with the rotating mirror. The position variation of the reflected beam from the mirror rotation was then monitored by the PSPD. Finally, the PSPD measured the amplified displacement as opposed to the actual movement of the stage via an optical lever mechanism, providing the ability to more precisely control the nanoscale stage. The displacement amplification process was modeled by structural analysis. The simulation results of the amplification ratio showed that the distance variation between the PSPD and the mirror plate as well as the length L of the mirror plate could be used as the basic design parameters for a SDS nano-stage. The PSPD was originally designed for a total travel range of 30 to 60 mm, and the SDS nano-stage amplified that range by a factor of 15 to 25. Based on these results, a SDS nano-stage was fabricated using principle of displacement amplification.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.168-175
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• 2003

In this research, a bridge-type flexure hinge mechanism is developed and optimized to amplify the displacement of a multilayer piezostack. Developed hinge mechanism has three-dimensional structure to reduce link size, so it have high amplification ratio with respect to small size. A flexure hinge is assumed to be 6 degree-of-freedom spring elements and matrix methods are used to model a hinge mechanism. To verify derived matrix model, a displacement and frequency experiments are performed. The analysis result shows that the displacemental error between matrix model and experiments is below 10 percents and the deformation of hinge in parasitic direction should be considered In hinge modeling. Using developed matrix model, an optimal design is performed to maximize the performance of hinge mechanism.

• Earthquakes and Structures
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• v.4 no.5
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• pp.557-585
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• 2013

The recent huge earthquake ground motion records in Japan result in the reconsideration of seismic design forces for nuclear power stations from the view point of seismological research. In addition, the seismic design force should be defined also from the view point of structural engineering. In this paper it is shown that one of the occurrence mechanisms of such large acceleration in recent seismic records (recorded in or near massive structures and not free-field ground motions) is due to the interaction between a massive building and its surrounding soil which induces amplification of local mode in the surface soil. Furthermore on-site investigation after earthquakes in the nuclear power stations reveals some damages of soil around the building (cracks, settlement and sand boiling). The influence of plastic behavior of soil is investigated in the context of interaction between the structure and the surrounding soil. Moreover the amplification property of the surface soil is investigated from the seismic records of the Suruga-gulf earthquake in 2009 and the 2011 off the Pacific coast of Tohoku earthquake in 2011. Two methods are introduced for the analysis of the non-stationary process of ground motions. It is shown that the non-stationary Fourier spectra can detect the temporal change of frequency contents of ground motions and the displacement profile integrated from its acceleration profile is useful to evaluate the seismic behavior of the building and the surrounding soil.

• Smart Structures and Systems
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• v.26 no.4
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• pp.481-493
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• 2020

The negative stiffness spring and inerter are both characterized by the negative stiffness effect in the force-displacement relationship, potentially yielding an amplifying mechanism for dashpot deformation by being incorporated with a series tuning spring. However, resisting forces of the two mechanical elements are dominant in different frequency domains, thus leading to necessary complementarity in terms of vibration control and the amplifying benefit. Inspired by this, this study proposes a Negative Stiffness Inerter System (NSIS) as an earthquake protection system and developed analytical design formulae by fully utilizing its advantageous features. The NSIS is composed of a sub-configuration of a negative stiffness spring and an inerter in parallel, connected to a tuning spring in series. First, closed-form displacement responses are derived for the NSIS structure, and a stability analysis is conducted to limit the feasible domains of NSIS parameters. Then, the dual advantageous features of displacement reduction and the dashpot deformation amplification effect are revealed and clarified in a parametric analysis, stimulating the establishment of a displacement-based optimal design framework, correspondingly yielding the design formulae in analytical form. Finally, a series of examples are illustrated to validate the derived formulae. In this study, it is confirmed that the synergistic incorporation of the negative stiffness spring and the inerter has significant energy dissipation efficiency in a wide frequency band and an enhanced control effect in terms of the displacement and shear force responses. The developed displacement-based design strategy is suitable to utilize the dual benefits of the NSIS, which can be accurately implemented by the analytical design formulae to satisfy the target vibration control with increased energy dissipation efficiency.

• Earthquakes and Structures
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• v.18 no.3
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• pp.297-312
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• 2020

The KiK-net by NIED is a vertical array measurement system. In the database of KiK-net, singular pulse waves were observed in the seismic record at the borehole of TTRH02 during the mainshock (the magnitude of Japan Meteorological Agency (M_J) 7.3, M_W 6.8) and aftershock (M_j 4.2) of Tottori-ken Seibu earthquake in 2000. Singular pulse waves were also detected in the seismic records at the borehole of IWTH25 during the Iwate-Miyagi Nairiku earthquake in 2008 (M_J 7.2, M_W 6.9). These pulse waves are investigated by using the wave shape analysis methods, e.g., the non-stationary Fourier spectra and the double integrated displacement profiles. Two types of vibration modes are discriminated as the occurrence mechanism of the singular pulse waves. One corresponds to the reversal points in the displacement profile with the amplitude from 10^-4 m to 10^-1 m, which is mainly related to the fault activity and the amplification pass including the mechanical amplification (collision) of the seismograph in the casing pipe. The other is the cyclic pulse waves in the interval of reversal points, which is estimated as the backlash of the seismograph itself with the amplitude from 10^-5 m to 10^-4 m.

• Earthquakes and Structures
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• v.17 no.1
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• pp.75-89
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• 2019

The paper presents experimental and numerical studies carried out on low-rise RC frames, typically found in developing countries. Shake table tests were conducted on 1:3 reduced scaled two-story RC frames that included a code conforming SMRF model and another non-compliant model. The later was similar to the code conforming model, except, it was prepared in concrete having strength 33% lower than the design specified, which is commonly found in the region. The models were tested on shake table, through multiple excitations, using acceleration time history of 1994 Northridge earthquake, which was linearly scaled for multi-levels excitations in order to study the structures' damage mechanism and measure the structural response. A representative numerical model was prepared in finite element based program SeismoStruct, simulating the observed local damage mechanisms (bar-slip and joint shear hinging), for seismic analysis of RC frames having weaker beam-column joints. A suite of spectrum compatible acceleration records was obtained from PEER for incremental dynamic analysis of considered RC frames. The seismic performance of considered RC frames was quantified in terms of seismic response parameters (seismic response modification, overstrength and displacement amplification factors), for critical comparison.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.348-354
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• 2003

This study outlines the analysis of toggle system and the vibration control performance when the toggle-rotational inertia damper system was applied to a structure. Numerical analysis shows that the relative displacement of the structure can be amplified by amplification mechanism of the toggle system and the capacity of the damper can be reduced without the loss of vibration control performance. It is also observed that vibration control effects is caused by the increase of equivalent mass due to the rotational inertia of damper.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.491-498
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• 2003

The purpose of this study is to analyze the geometric nonlinearity of a toggle system and to evaluate the vibration control performance when the toggle system with a viscous damper was applied to a structure. Numerical analysis shows that the relative displacement of the structure can be amplified by amplification mechanism of the toggle system and the capacity of the damper can be reduced without the loss of vibration control performance. It is also observed that the geometric nolinearity of toggle system using the linear viscous damper has little effect on the performance.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1281-1286
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• 2013

In this paper, a miniaturized stage with two prismatic-prismatic joints (2-PP) type parallel compliant mechanism driven by piezo actuators is proposed. This stage consists of two layers which are a motion guide layer and an actuation layer. The motion guide layer has 2-PP type parallel compliant mechanism to guide two translational motions, whereas the actuation layer has two leverage type amplification mechanisms and two piezo actuators to generate forces. Since the volume of the stage is too small to mount displacement sensors, the piezo actuators embedding strain gauge sensors are chosen. With the strain gauge-embedded piezo actuators, a semi-control is implemented, which results in hysteresis compensation of the stage. As the results, the operating range of $30{\mu}m$, the resolution of 20 nm, and the bandwidth of 400 Hz in each axis were obtained in the experiments.