• 센서학회지
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• 제21권3호
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• pp.235-239
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• 2012

This paper presents frequency response compensation technique, and a self-oscillation circuit for capacitive microresonator with the compensation technique using programmable capacitor array, to compensate for the frequency response distorted by parasitic capacitances, and to obtain stable oscillation condition. The parasitic capacitances between the actuation input port and capacitive output port distort the frequency response of the microresonator. The distorted non-ideal frequency response can be compensated using two programmable capacitor arrays, which are connected between anti-phased actuation input port and capacitive output port. The simulation model includes the whole microresonator system, which consists of mechanical structure, transimpedance amplifier with automatic gain control, actuation driver and compensation circuit. The compensation operation and oscillation output of the system is verified with the simulation results.

• 드라이브 ㆍ 컨트롤
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• 제18권1호
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• pp.17-23
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• 2021

The flow signal or spool position signal is used to determine the dynamic characteristics of directional control valves. Alternatively, the signal of spool position or flow can be replaced with the velocity of a low friction, low inertia actuator. In this study, the frequency response of the servo valve equipped with a spool position transducer is measured with a metering cylinder. The input signal, spool displacement, load pressure, and velocity of the metering cylinder are measured, and the theoretical results from the transfer function analysis are verified. The superposition rule for magnitude ratio and phase angle was found to be always applicable among any signal type, and it was found that the load pressure signal is not appropriate for use as the signal for measuring the frequency response of a servo valve. It was confirmed that the frequency response of a servo valve using metering cylinder was similar to the results from a spool displacement signal. The metering cylinder used for measuring the frequency response of a servo valve should be designed to have sufficiently greater bandwidth frequency than the bandwidth frequency of the servo valve.

• Structural Engineering and Mechanics
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• 제75권3호
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• pp.311-325
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• 2020

In applying the spectral stochastic finite element methods to the frequency response analysis, the conventional methods are known to give unstable and inaccurate results near the natural frequencies. To address this issue, a new sensitivity based stabilized formulation for stochastic frequency response analysis is proposed in this paper. The main difference over the conventional spectral methods is that the polynomials of random variables are applied to both numerator and denominator in approximating the harmonic response solution. In order to reflect the resonance behavior of the structure, the denominator polynomials is constructed by utilizing the natural frequency sensitivity and the random mode superposition. The numerator is approximated by applying a polynomial chaos expansion, and its coefficients are obtained through the Galerkin or the spectral projection method. Through various numerical studies, it is seen that the proposed method improves accuracy, especially in the vicinities of structural natural frequencies compared to conventional spectral methods.

• Structural Engineering and Mechanics
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• 제39권6호
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• pp.877-893
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• 2011

Response spectra of earthquake ground motions are important in the earthquake-resistant design and reliability analysis of structures. The formulation of the response spectrum in the frequency domain efficiently computes and evaluates the stochastic response spectrum. The frequency information of the excitation can be described using different functional forms. The shapes of the calculated response spectra of the excitation show strong magnitude and site dependency, but weak distance dependency. In this paper, to compare the effect of the earthquake ground motion variables, the contribution of these sources of variability to the response spectrum's uncertainty is calculated by using a stochastic analysis. The analytical results show that earthquake source factors and soil condition variables are the main sources of uncertainty in the response spectra, while path variables, such as distance, anelastic attenuation and upper crust attenuation, have relatively little effect. The presented formulation of dynamic structural response in frequency domain based only on the frequency information of the excitation can provide an important basis for the structural analysis in some location that lacks strong motion records.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.467-472
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• 2007

A modern MEMS resonator is a micro-scale structure operated over a high frequency range. In order to predict its resonant behavior in a design process, High-frequency response analysis (Hi-FRA) is demanded. Algebraic substructuring (AS) is known as a fast numerical technique to construct an eigenspace for FR and frequency sweep (FS) algorithm efficiently solves the frequency response system projected on the eigenspace. However, the existing FS algorithm using AS is developed for low-FRA, say over the range 1Hz-2KHz. In this work, we extend the FS algorithm using AS for FRA over an arbitrary frequency range. Therefore, it can be efficiently applied to systems operated at a high frequency, say over the range 230MHz-250MHz. The success of the proposed method is demonstrated by Hi-FRA of a checkerboard resonator.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.35-42
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• 2002

Frequency responses for most of the local seismic sensors in Korea have been roughly checked by mutual comparison of Fourier spectra of seismic records from accelerometer and seismometer, both of which are installed at the same location. Especially, because the frequency content of the seismic energy is usually above 1 Hz for local earthquakes, the reliability of low frequency response could have not been evaluated. Fortunately a recent large earthquake, Ms=7.2 on 02/06/29 containing dominant low frequency energy makes it possible to check the low frequency response of the seismic sensors, especially EpiSensor and JC-V100. Considering two types of sensor pairs, (STS-2 and EpiSensor, JC-V100 and EpiSensor), the low frequency response of EpiSensor is confirmed first by comparison with STS-2 which has proved low frequency response. Second, reliable low frequency limit of instrumentally corrected seismic data from JC-V100 data is estimated to be about 0.03 Hz by comparison with EpiSensor data.

• 한국공작기계학회논문집
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• 제12권1호
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• pp.92-100
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• 2003

Using a quarter car model, an analytic method for performance estimation of a vehicle suspension system with respect to frequency response, RMS response and performance index is presented. From frequency response function, compromization of response performance to the whole frequency range is verified and from RMS response and performance index, sensitivity of ride md handling characteristics are examined. Using a full car model, sweet area(stable ride area) are determined and performance sensitivity is estimated according to the change of feedback gains. In order to esimate the output sensitivity, response we is displayed using a 3-dimensional contour plot. Design data n suggested for optimal design parameter esimation, which maximize the performance of the given suspension system.

• 한국공간구조학회논문집
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• 제15권2호
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• pp.113-120
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• 2015

This study investigate the dynamic response changes of rib dome structure according to property changes of Substructure. Eigenvalue analysis is conducted in first natural frequency of rib dome versus substructure and searched in the dominant mode of horizontal and vertical direction. Resonance frequency by each first natural frequency of the rib dome structure, substructure and total structure is applied for a seismic wave. That is analyzed about maximum displacement response ratio and maximum acceleration response ratio.

• 산업기술연구
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• 제16권
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• pp.239-245
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• 1996

Modal parameters determine the frequency response characteristics of vibration system or acoustic system. When the two systems are fully coupled, however, coupling changes the vibrational and acoustic model parameters into those of the coupled system. In this case, it is very difficult to obtain the modified model parameters and response characteristics. In this paper, coupling effect is analytically investigated on the natural frequency, mode and frequency response characteristics. The result can be applied to understand and to design the frequency response characteristics of the vehicle passenger compartment.

• Structural Engineering and Mechanics
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• 제10권1호
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• pp.17-26
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• 2000

This paper presents a case study with a multi-degree-of-freedom (MDOF) system where the Floor Response Spectra (FRS) have been derived from a large ensemble of ground motion accelerograms. The FRS are evaluated by the frequency response function which is calculated numerically. The advantage of this scheme over a repetitive time-history analysis of the entire structure for each accelerogram of the set has been highlighted. The present procedure permits generation of FRS with a specified probability of exceedence.