• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1190-1199
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• 2010

This paper reports active control of clamped beams using acceleration feedback controllers (AF). The equations of motion of clamped beam under force and moment pairs were derived and the equations of AF controllers were formulated. The effect of the parameters - gain and damping ratio - of the AF controllers on the open loop transfer function was investigated mainly in terms of the system stability. Increasing the gain of the AF controller tuned at a mode, the magnitude of the open loop transfer function is increased at all frequencies. The increase of the damping ratio of the AF controller leads to decrease the magnitude of the open loop transfer function and modifies its phase characteristics to be more stable. Three AF controllers connected in parallel were then proposed. Each AF controller is tuned at the 2nd, 3rd and 4th modes, respectively. Their parameters were determined to remain the system to be stable based on the results of the parametric study. A significant reduction in vibration at the 3 modes can be obtained.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.2
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• pp.14-22
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• 1995

We treat the vibrations of circular beam and make use of the method employed by J.T.Tielking, which is based on the principle of Hamilton. The Hamilton's principle requires the determinations of the potential and the kinetic energy of the model as well as done by internal pressure forces. Thje potential energy is composed of a part due to elastic deformations of the beam and a part due to radial and tangential displacements of the tread band with respect to the wheel rim. The equations of motion for such a model are derived by reference to conventional energy method. The accuracy of the expressions is demonstrated by comparison of calculated and experimental natural frequencies for circular beam. The circular beam experiences a harmonic, radial excitat- ion acting at a fixed point on the beam. Modal parameters varying the inflation pressure and load are determined experimentally by using the transfer function method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.601-605
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• 2007

This paper describes the experimental method to monitor the structural integrity. The crack on structures changes the wave propagation characteristics of structures. To monitor this change, frequency dependent variation of dynamic stiffness of beam structures is obtained by using beam transfer function method, and its trends are compared to undamaged one for identifying the location and size of the crack. Piezoelectric actuators were used to generate flexural vibrations. It eliminated various restrictions of continuously measuring wave propagation characteristics and monitoring structural integrity. The structural integrity was identified with minimal number of measurements and smart structures employing PZT actuations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.217-224
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• 2016

In this study, a transfer matrix method (TMM) for a twisted uniform beam considering the effect of rotary inertia is developed, and the differential equation and the displacements and forces are derived from Hamilton's principle. The particular transfer matrix is derived by applying the distributed mass and transcendental function while using a local coordinate system. In addition, the results obtained from this method are independent for a number of subdivided elements, and this method can determine the exact solutions for the free vibration characteristics of a twisted uniform Rayleigh beam. To validate the accuracy of the proposed TMM, the computed results are compared with those reported in the existing literature, and the comparison results indicate notably good agreement. In addition, the method is used to investigate the effects of rotary inertia for a twisted beam.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.3
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• pp.19-32
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• 2003

In the conventional photorefractive joint transform correlator(PRJTC), the intensity ration of input signal-to-pump beam should be large enough to saturate two-beam coupling transfer function to obtain a desired correlation result. As a result, the signal-to-noise ratio(SNR) of correlation result is decreased in a noisy input image. In this paper, we propose the improved method for increasing the SNR of the PRJTC by using the characteristics of BaTiO$_3$. We stop the energy transfer saturating by low intensity ratio of input beam and realize a short length of effective interaction in BaTiO$_3$ by making large incident angle of the signal beam. So the gain in high frequency area is decreased and the gain in low frequency area comes up to the saturation gain of the beam coupling transfer function. Therefore the SNR is improved in noisy input image and the PRJTC can be easily realized by low intensity ratio of input beam.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.171-176
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• 2001

Recent building structures are superior in its ability but they are light and flexible, and so have problems of vibration. In general, the problem of vertical vibration is not considered in structural design. However, in terms of serviceability for inhabitants in buildings, the estimation of vibration in design stage is important. Characteristics of vertical vibration is changed by modeling method of beam-column joint. To check the characteristics of vertical vibration, many tests and analyses were conducted on constructing building in Seoul. Results of tests and analyses were compared using transfer function. As a results, to check the vertical vibration, the cramp ratio of beam-column joint must be considered and reduced in structural design.

• Korean Journal of Optics and Photonics
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• v.6 no.2
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• pp.101-107
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• 1995

To investigate the diffraction property of the Bessel beam for defocus which acts CFAP (Combined Filter of Amplitude and Phase), we calculated numerically the intensity, the radius of central spot, and the optical transfer function for the number of node of the Bessel beam when an optical system has an aberration-free or a spherical aberration. The Bessel beam has larger the maximum intensity and the OTF value for an optical system with a spherical aberration than that with an aberrationfree. Particularly, the OTF value at the point of maximum intensity for $W_{40}=3\lambda$is higher for the Bessel beam than for the Clear aperture. From these results, we know that the Bessel beam has the compensating effect. The Bessel beam also has the radius of central spot having a superresolution. We will useful for the fabrication of semiconductor device and the optical recording system using these effects.ffects.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.87.5-87
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• 2001

In the past, we presented the tracking system with one sampling delay. In this paper, first we propose a tracking system with N-th sampling delay, in the case where an input-output pulse transfer function of a plant Z$\_$-N/. Secondly we propose a system configuration converting an input-output pulse transfer function of a plant into Z$\_$-N/ with the inverse system of the plant. Moreover, the proposed tracking system configuration is applied to an actual Ball and Beam system and good results are obtained.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.248-256
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• 1993

This paper deriver the generalized mass to find dynamic characteristics and its derivatives of a continous system. And a new sensitivity analysis method is presented by using the amount of change of generalized mass and vibrational mode caused by the variation of lumped and distributed mass. In this paper, to get or detect appropriate results, cantilever beam and stepped beam are used. Deviations of sensitivity coefficient, natual frequency, vibrational mode and transfer function are calculated as result, and compared with the theoretical exact values.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.566-572
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• 2000

The System identification is the process of developing or improving a mathematical model of a physical system using experimental data of the input, output and noise relationship. The field of system identification has been an important discipline within the automatic control area. The reason is the requirement that mathematical models having a specified accuracy must be used to apply modem control methods. In this paper, it is confirmed that we can obtain transfer function of flexible beam that is expressed in the forms of identified state-space system matrix A, B, C, D and identified observer gain G using Eigensystem Realization Algorithm including singular value decomposition. And these matrices can be applied to the automatic control. In addition to, it is also confirmed that transfer function can express a system using identified observer gain G, in spite of a noisy data or a periodic disturbance.