• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.3 s.22
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• pp.73-82
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• 2005

This paper describes shock waveform synthesis methods for a shock response spectnlm over a short time interval with which intereference between parts within a test item is increased to perform a sufficient shock test for damage or malfunction which may be caused by the interference between parts, and a digital filter for obtaining a shock response history required for the shock waveform synthesis and a digital inverse filter for restoration by inversely using the digital filter. The time at which the maximax value occurs in the response history is detected in order to establish a delay time which is one of the parameters in the wavelet, on the condition that the natural frequency of SDOF system with a Q (quality factor) of 10 equals to the wavelet frequency of the zero delay wavelet input. A shock response spectrum over a short time interval and an abrupt change in the acceleration for an instant are illustrated as features of the synthesized waveform.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.324-330
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• 1990

In this study, in order to perform dynamic design of machine tools reasonably and effectively, a method was formulated to be applicable to the damped structures connected by joints having elasticity and damping by using substructure synthesis method. And a nonlinear solution method was proposed and it formulates the nonlinear parts by describing functions and uses the reducing transformation matrix by the substructure synthesis method. The results of frequency response analysis of a machine tool, where an NC lathe was partitioned by three parts of spindle, housing and bed-base part and the nonlinearity of bearing parts between spindle and housing was modelled, showed force dependency of the response.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.12
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• pp.3782-3791
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• 1996

A great deal of effert has been invested in upgrading the performance and the efficiency of mechanical structures. Using experimental modal analysis(EMA) or finite element analysis(FEA) data of mechanical structures, this performance and efficiency can be effectively evaluated. In order to analyze complex structures such as automobiles and aircraft, for the sake of computing efficiency, the dynamic substructuring techniques that allow to predict the dynamic behavior of a structure based on that of the composing structures, are widely used. By llinking a modal model obtained from EMA and an analytical model obtained from FEA, the best conditioned structures can be desinged. In this paper, a new algorithm for structural dynamic modification-SRFSM (substructure response function sensitivity method) is proposed by linking frequency responce function synthesis and response function sensitivity. A mehtod to obtain response function sensitivity using direct derivative of mechanical impedance, is also used.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.3
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• pp.122-127
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• 2005

The styling of automobile wheels and their effect on vehicle appearance has increased in importance in recent years. The wheel designer has been given the task of insuring that a wheel design meets its engineering objectives without affecting the styling theme. The wheel and tire system is considered as a vehicle component whose dynamic modal information of the tire/wheel system are employed in the modal synthesis model of the vehicle. The vibration characteristics of a automobile wheel play an important role to judge a ride comfort and quality for a automobile. In this paper, the vibration characteristics of a Al-alloy and steel wheel for automobile are studied. Natural frequency, damping and mode shape are determined experimentally by frequency response function method. Results show that wheel material property, size and design are parameter for shift of natural frequency and damping.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.623-628
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• 2001

The styling of passenger car wheels and their effect on vehicle appearance has increased in importance in recent years. The wheel designer has been given the task of insuring that a wheel design meets its engineering objectives without affecting the styling theme. The wheel and tire system is considered as a vehicle component whose dynamic modal information of the tire/wheel system are employed in the modal synthesis model of the vehicle. The Vibration characteristics of a passenger car wheel play an important role to judge a ride comfortability and quality for a passenger car. In this paper, the vibration characteristics of a AI-alloy and steel wheel for passenger car are studied. Natural frequency, damping and mode shape are determined experimentally by frequency response function method. Results show that wheel material property, size and design are parameter for shift of natural frequency and damping.

• Journal of KSNVE
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• v.8 no.1
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• pp.180-186
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• 1998

Vibration test fixture is used in random vibration control testing. The specified reference spectrum should be transmitted equally to the specimen attachment points on the fixture. In most practical cases, however, spectrum at each of specimen attachment points may be quite different from the specified reference spectrum because of the dynamic characteristics of vibration test fixture. This paper proposes the method of experimental dynamic modification of fixture system for vibration test so that the reference spectrum can be transmitted to the specimen attachment points without distortion. The stiffness of mounts of specimen and the thickness of fixture are considered as design variables. The frequency response functions of specimen used for input data are obtained from vibration testing, and the frequency response functions of fixture are obtained from finite element modeling. The sensitivities of frequency response functions at specimen attachment points to the mount stiffness are derived from synthesis method of transfer function. And the sensitivities to the thickness of fixture are also derived from finite element modeling. The presented method is verified by computer simulation and vibration testing.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.560-568
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• 1998

Recently to develop an automobile with better properities many researches and investments have been executed. In this paper we intend to improve the automobile properties by reducing the weight of the engine without changing the dynamic characteristics. At first the vibration analysis by the Substructure Synthesis Mehtod and the exciting test of the engine model performed to confirm the reliability of the analyzing tools. And the weight minimiza-tion is performed by the Sensitivity Analysis and the Optimum Structural Modificationl. To decrease the engine weight ideally the weight of the parts with the low sensitivity is to cut mainly and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with the high sensitivity. As actually the mathematical unique solution for the homogeneous problem(i. e. 0 object func-tion problem)does not exist we redesign the engine block with much thinner initial thickness and recover the natural frequencies and natural modes of original structure by the sensitivity analy-sis and then observe the Frequency Response Function(FRF) for the interesting points. In this analysis the original thickness of the engine model is 8mm and the redesigned initial thicknesses are 5mm and 6mm, And the number of the interesting natural frequencies are 1, 2, 3, 4 and 5 respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1869-1875
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• 2008

Recently, a direct data-driven synthesis of a proportional integral derivative(PID) controller for a linear time-invariant(LTI) plant was presented in [1]. The authors showed that a complete set of PID controllers achieving robust performance and stability can be calculated directly from frequency response(FR) data without an identified transfer function model. However, it is not convenient to use this method because it requires complicated numerical algorithms to find specific frequencies which are solutions of an identical equation. The method also requires determination of the boundary of the controller's parameters from a finite set of FR data. In this paper, we present the development of a user-friendly Matlab toolbox based on the method in [1]. This toolbox allows us to obtain a complete three-dimensional(3-D) graphical solution of PID controllers that meet multiple design objectives. Several examples are given to demonstrate the use of the toolbox.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.52-57
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• 2000

This study intends to reduce the weight of structure without changing the dynamic characteristics. At first, the Vibration analysis by the Substructure Synthesis Method and FFM using the ANSYS are performed for the engine speed converter to confirm the reliability of the analyzing tools. Weight minimization is performed by the Sensitivity Analysis and the Optimum Structural Modification. To decrease the converter weight ideally, the parts with low sensitivity are to be cut mainly, and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with high sensitivity. As the unique mathematical solution for the homogeneous problem(i.e. 0 object function problem) does not exist, the converter is redesigned with much thinner initial thickness. The goal of this study is to recover the dynamic characteristics of redesigned structure to those of the original one. To say in the other words, the modified structure has the same dynamic characteristics and the more lighter weight to compare with the original one.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.161-166
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• 2001

This study intends to reduce the weight of structure without changing the dynamic characteristics. At first, the Vibration analyses by the Substructure Synthesis Method and FEM using the ANSYS are performed for the engine speed converter to confirm the reliability of the analyzing tools. Weight minimization is performed by the Sensitivity Analysis and the Optimum Structural Modification. To decrease the converter weight ideally, the parts with low sensitivity are to be cut mainly, and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with high sensitivity. As the unique mathematical solution for the homogeneous problem( i.e. 0 object function problem) does not exist, the converter is redesigned with much thinner initial thickness. The goal of this study is to recover the dynamic characteristics of redesigned structure to those of the original one. To say in the other words, the modified structure has the same dynamic characteristics and the more lighter weight to compare with the original one. In this analysis, the modification was performed with the redesigned initial thickness of 60 mm and 70 mm. And the numbers of the interesting natural frequencies are 1, 2, 4 respectively. Consequently 27％ of weight reduction effects were earned.